A comparative study of the mechanical behaviour of thermally oxidised commercially pure titanium and zirconium.

PubMed

Alansari, A; Sun, Y

2017-10-01

The objective of this study is to compare the mechanical behaviour of thermally oxidised commercially pure titanium (CP-Ti) and commercially pure zirconium (CP-Zr). For this purpose, these two bio-metals were thermally oxidised under the same condition (650°C for 6h) and the oxidised specimens were characterised using various analytical and experimental techniques, including oxygen uptake analysis, layer thickness and hardness measurements, scratch tests, dry sliding friction and wear tests and tribocorrosion tests in Ringer's solution. The results show that under the present thermal oxidation condition, 4 times more oxygen is introduced into CP-Zr than into CP-Ti and the oxide layer produced on CP-Zr is nearly 6 times thicker than that on CP-Ti. Thermally oxidised CP-Zr possesses a higher hardness, a deeper hardening depth and better scratch resistance than thermally oxidised CP-Ti. Under dry sliding and tribocorrosion conditions, thermally oxidised CP-Zr also possesses much better resistance to material removal and a higher load bearing capacity than thermally oxidised CP-Ti. Thus, thermally oxidised Zr possesses much better mechanical behaviour than thermally oxidised Ti. Copyright © 2017 Elsevier Ltd. All rights reserved.

Oxidation and methylation of dissolved elemental mercury by anaerobic bacteria

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Haiyan; Lin, Hui; Zheng, Wang

2013-08-04

Methylmercury is a neurotoxin that poses significant health risks to humans. Some anaerobic sulphate- and iron-reducing bacteria can methylate oxidized forms of mercury, generating methylmercury1-4. One strain of sulphate-reducing bacteria (Desulfovibrio desulfuricans ND132) can also methylate elemental mercury5. The prevalence of this trait among different bacterial strains and species remains unclear, however. Here, we compare the ability of two strains of the sulphate-reducing bacterium Desulfovibrio and one strain of the iron-reducing bacterium Geobacter to oxidise and methylate elemental mercury in a series of laboratory incubations. Experiments were carried out under dark, anaerobic conditions, in the presence of environmentally-relevant concentrations ofmore » elemental mercury. We report differences in the ability of these organisms to oxidise and methylate elemental mercury. In line with recent findings5, we show that Desulfovibrio desulfuricans ND132 can both oxidise and methylate elemental mercury. However, the rate of methylation of elemental mercury is only about one third the rate of methylation of oxidized mercury. We also show that Desulfovibrio alaskensis G20 can oxidise, but not methylate, elemental mercury. Geobacter sulfurreducens PCA is able to oxidise and methylate elemental mercury in the presence of cysteine. We suggest that the activity of methylating and non-methylating bacteria may together enhance the formation of methylmercury in anaerobic environments.« less

Multitechnique characterisation of 304L surface states oxidised at high temperature in steam and air atmospheres

NASA Astrophysics Data System (ADS)

Mamede, Anne-Sophie; Nuns, Nicolas; Cristol, Anne-Lise; Cantrel, Laurent; Souvi, Sidi; Cristol, Sylvain; Paul, Jean-François

2016-04-01

In case of a severe accident occurring in a nuclear reactor, surfaces of the reactor coolant system (RCS), made of stainless steel (304L) rich in Cr (>10%) and Ni (8-12%), are oxidised. Fission products (FPs) are released from melt fuel and flow through the RCS. A part of them is deposited onto surfaces either by vapour condensation or by aerosol deposition mechanisms. To be able to understand the nature of interactions between these FPs and the RCS surfaces, a preliminary step is to characterize the RSC surface states in steam and air atmosphere at high temperatures. Pieces of 304L stainless steel have been treated in a flow reactor at two different temperatures (750 °C and 950 °C) for two different exposition times (24 h and 72 h). After surfaces analysing by a unique combination of surface analysis techniques (XPS, ToF-SIMS and LEIS), for 304L, the results show a deep oxide scale with multi layers and the outer layer is composed of chromium and manganese oxides. Oxide profiles differ in air or steam atmosphere. Fe2O3 oxide is observed but in minor proportion and in all cases no nickel is detected near the surface. Results obtained are discussed and compared with the literature data.

Tracing iron-carbon redox from surface to core

NASA Astrophysics Data System (ADS)

McCammon, C. A.; Cerantola, V.; Bykova, E.; Kupenko, I.; Bykov, M.; Chumakov, A. I.; Rüffer, R.; Dubrovinsky, L. S.

2017-12-01

Numerous redox reactions separate the Earth's oxidised surface from its reduced core. Many involve iron, the Earth's most abundant element and the mantle's most abundant transition element. Most iron redox reactions (although not all) also involve other elements, including carbon, where iron-carbon interactions drive a number of important processes within the Earth, for example diamond formation. Many of the Earth's redox boundaries are sharp, much like the seismic properties that define them, for example between the lower mantle and the core. Other regions that appear seismically homogeneous, for example the lower mantle, harbour a wealth of reactions between oxidised and reduced phases of iron and carbon. We have undertaken many experiments at high pressure and high temperature on phases containing iron and carbon using synchrotron-based X-rays to probe structures and iron oxidation states. Results demonstrate the dominant role that crystal structures play in determining the stable oxidation states of iron and carbon, even when oxygen fugacity (and common sense) would suggest otherwise. Iron in bridgmanite, for example, occurs predominantly in its oxidised form (ferric iron) throughout the lower mantle, despite the inferred reducing conditions. Newly discovered structures of iron carbonate also stabilise ferric iron, while simultaneously reducing some carbon to diamond to balance charge. Other high-pressure iron carbonates appear to be associated with the emerging zoo of iron oxide phases, involving transitions between ferrous and ferric iron through the exchange of oxygen. The presentation will trace redox relations between iron and carbon from the Earth's surface to its core, with an emphasis on recent experimental results.

Hydrogen peroxide-mediated oxidative stress disrupts calcium binding on calmodulin: More evidence for oxidative stress in vitiligo

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schallreuter, K.U.; Gibbons, N.C.J.; Zothner, C.

Patients with acute vitiligo have low epidermal catalase expression/activities and accumulate 10{sup -3} M H{sub 2}O{sub 2}. One consequence of this severe oxidative stress is an altered calcium homeostasis in epidermal keratinocytes and melanocytes. Here, we show decreased epidermal calmodulin expression in acute vitiligo. Since 10{sup -3}M H{sub 2}O{sub 2} oxidises methionine and tryptophan residues in proteins, we examined calcium binding to calmodulin in the presence and absence of H{sub 2}O{sub 2} utilising {sup 45}calcium. The results showed that all four calcium atoms exchanged per molecule of calmodulin. Since oxidised calmodulin looses its ability to activate calcium ATPase, enzyme activitiesmore » were followed in full skin biopsies from lesional skin of patients with acute vitiligo (n = 6) and healthy controls (n = 6). The results yielded a 4-fold decrease of ATPase activities in the patients. Computer simulation of native and oxidised calmodulin confirmed the loss of all four calcium ions from their specific EF-hand domains. Taken together H{sub 2}O{sub 2}-mediated oxidation affects calcium binding in calmodulin leading to perturbed calcium homeostasis and perturbed L-phenylalanine-uptake in the epidermis of acute vitiligo.« less

Mantle to surface degassing of alkalic magmas at Erebus volcano, Antarctica

USGS Publications Warehouse

Oppenheimer, C.; Moretti, R.; Kyle, P.R.; Eschenbacher, A.; Lowenstern, J. B.; Hervig, R.L.; Dunbar, N.W.

2011-01-01

Continental intraplate volcanoes, such as Erebus volcano, Antarctica, are associated with extensional tectonics, mantle upwelling and high heat flow. Typically, erupted magmas are alkaline and rich in volatiles (especially CO2), inherited from low degrees of partial melting of mantle sources. We examine the degassing of the magmatic system at Erebus volcano using melt inclusion data and high temporal resolution open-path Fourier transform infrared (FTIR) spectroscopic measurements of gas emissions from the active lava lake. Remarkably different gas signatures are associated with passive and explosive gas emissions, representative of volatile contents and redox conditions that reveal contrasting shallow and deep degassing sources. We show that this unexpected degassing signature provides a unique probe for magma differentiation and transfer of CO2-rich oxidised fluids from the mantle to the surface, and evaluate how these processes operate in time and space. Extensive crystallisation driven by CO2 fluxing is responsible for isobaric fractionation of parental basanite magmas close to their source depth. Magma deeper than 4kbar equilibrates under vapour-buffered conditions. At shallower depths, CO2-rich fluids accumulate and are then released either via convection-driven, open-system gas loss or as closed-system slugs that ascend and result in Strombolian eruptions in the lava lake. The open-system gases have a reduced state (below the QFM buffer) whereas the closed-system gases preserve their deep oxidised signatures (close to the NNO buffer). ?? 2011 Elsevier B.V.

Application of a Novel Functional Gene Microarray to Probe the Functional Ecology of Ammonia Oxidation in Nitrifying Activated Sludge

PubMed Central

Short, Michael D.; Abell, Guy C. J.; Bodrossy, Levente; van den Akker, Ben

2013-01-01

We report on the first study trialling a newly-developed, functional gene microarray (FGA) for characterising bacterial and archaeal ammonia oxidisers in activated sludge. Mixed liquor (ML) and media biofilm samples from a full-scale integrated fixed-film activated sludge (IFAS) plant were analysed with the FGA to profile the diversity and relative abundance of ammonia-oxidising archaea and bacteria (AOA and AOB respectively). FGA analyses of AOA and AOB communities revealed ubiquitous distribution of AOA across all samples – an important finding for these newly-discovered and poorly characterised organisms. Results also revealed striking differences in the functional ecology of attached versus suspended communities within the IFAS reactor. Quantitative assessment of AOB and AOA functional gene abundance revealed a dominance of AOB in the ML and approximately equal distribution of AOA and AOB in the media-attached biofilm. Subsequent correlations of functional gene abundance data with key water quality parameters suggested an important functional role for media-attached AOB in particular for IFAS reactor nitrification performance and indicate possible functional redundancy in some IFAS ammonia oxidiser communities. Results from this investigation demonstrate the capacity of the FGA to resolve subtle ecological shifts in key microbial communities in nitrifying activated sludge and indicate its value as a tool for better understanding the linkages between the ecology and performance of these engineered systems. PMID:24155925

Bimetallic Cu-Ni nanoparticles supported on activated carbon for catalytic oxidation of benzyl alcohol

NASA Astrophysics Data System (ADS)

Kimi, Melody; Jaidie, Mohd Muazmil Hadi; Pang, Suh Cem

2018-01-01

A series of bimetallic copper-nickel (CuNix, x = 0.1, 0.2, 0.5 and 1) nanoparticles supported on activated carbon (AC) were prepared by deposition-precipitation method for the oxidation of benzyl alcohol to benzaldehyde using hydrogen peroxide as oxidising agent. Analyses by means of X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) confirmed that Cu and Ni was successfully added on the surface of activated carbon. CuNi1/AC showed the best catalytic activity for the oxidation of benzyl alcohols to the corresponding aldehyde within a short reaction period at 80 °C. The catalytic performance is significantly enhanced by the addition of equal amount of Ni as compared to the monometallic counterpart. This result indicates the synergistic effect between Ni and Cu particles in the catalytic oxidation reaction.

Effects of Non-Indigenous Oysters on Microbial Diversity and Ecosystem Functioning

PubMed Central

Green, Dannielle S.; Boots, Bas; Crowe, Tasman P.

2012-01-01

Invasive ecosystem engineers can physically and chemically alter the receiving environment, thereby affecting biodiversity and ecosystem functioning. The Pacific oyster, Crassostrea gigas, invasive throughout much of the world, can establish dense populations monopolising shorelines and possibly altering ecosystem processes including decomposition and nutrient cycling. The effects of increasing cover of invasive C. gigas on ecosystem processes and associated microbial assemblages in mud-flats were tested experimentally in the field. Pore-water nutrients (NH4 + and total oxidised nitrogen), sediment chlorophyll content, microbial activity, total carbon and nitrogen, and community respiration (CO2 and CH4) were measured to assess changes in ecosystem functioning. Assemblages of bacteria and functionally important microbes, including methanogens, methylotrophs and ammonia-oxidisers were assessed in the oxic and anoxic layers of sediment using terminal restriction length polymorphism of the bacterial 16S rRNA, mxaF, amoA and archaeal mcrA genes respectively. At higher covers (40 and 80%) of oysters there was significantly greater microbial activity, increased chlorophyll content, CO2 (13 fold greater) and CH4 (6 fold greater) emission from the sediment compared to mud-flats without C. gigas. At 10% cover, C. gigas increased the concentration of total oxidised nitrogen and altered the assemblage structure of ammonia-oxidisers and methanogens. Concentrations of pore-water NH4 + were increased by C. gigas regardless of cover. Invasive species can alter ecosystem functioning not only directly, but also indirectly, by affecting microbial communities vital for the maintenance of ecosystem processes, but the nature and magnitude of these effects can be non-linear, depending on invader abundance. PMID:23144762

Surface Modification of Boron-Doped Diamond with Microcrystalline Copper Phthalocyanine: Oxygen Reduction Catalysis.

PubMed

Gan, Patrick; Foord, John S; Compton, Richard G

2015-10-01

Surface modification of boron-doped diamond (BDD) with copper phthalocyanine was achieved using a simple and convenient dropcast deposition, giving rise to a microcrystalline structure. Both unmodified and modified BDD electrodes of different surface terminations (namely hydrogen and oxygen) were compared via the electrochemical reduction of oxygen in aqueous solution. A significant lowering of the cathodic overpotential by about 500 mV was observed after modification of hydrogen-terminated (hydrophobic) diamond, while no voltammetric peak was seen on modified oxidised (hydrophilic) diamond, signifying greater interaction between copper phthalocyanine and the hydrogen-terminated BDD. Oxygen reduction was found to undergo a two-electron process on the modified hydrogen-terminated diamond, which was shown to be also active for the reduction of hydrogen peroxide. The lack of a further conversion of the peroxide was attributed to its rapid diffusion away from the triple phase boundary at which the reaction is expected to exclusively occur.

Links between seawater flooding, soil ammonia oxidiser communities and their response to changes in salinity.

PubMed

Nacke, Heiko; Schöning, Ingo; Schindler, Malte; Schrumpf, Marion; Daniel, Rolf; Nicol, Graeme W; Prosser, James I

2017-11-01

Coastal areas worldwide are challenged by climate change-associated increases in sea level and storm surge quantities that potentially lead to more frequent flooding of soil ecosystems. Currently, little is known of the effects of inundation events on microorganisms controlling nitrification in these ecosystems. The goal of this study was to investigate the impact of seawater flooding on the abundance, community composition and salinity tolerance of soil ammonia oxidisers. Topsoil was sampled from three islands flooded at different frequencies by the Wadden Sea. Archaeal ammonia oxidiser amoA genes were more abundant than their betaproteobacterial counterparts, and the distribution of archaeal and bacterial ammonia oxidiser amoA and 16S rRNA gene sequences significantly differed between the islands. The findings indicate selection of ammonia oxidiser phylotypes with greater tolerance to high salinity and slightly alkaline pH (e.g. Nitrosopumilus representatives) in frequently flooded soils. A cluster phylogenetically related to gammaproteobacterial ammonia oxidisers was detected in all samples analysed in this survey. Nevertheless, no gammaprotebacterial amoA genes could be amplified via PCR and only betaproteobacterial ammonia oxidisers were detected in enrichment cultures. A slurry-based experiment demonstrated the tolerance of both bacterial and archaeal ammonia oxidisers to a wide range of salinities (e.g. Wadden Sea water salinity) in soil naturally exposed to seawater at a high frequency. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Total knee arthroplasty with an oxidised zirconium femoral component: ten-year survivorship analysis.

PubMed

Ahmed, I; Salmon, L J; Waller, A; Watanabe, H; Roe, J P; Pinczewski, L A

2016-01-01

Oxidised zirconium was introduced as a material for femoral components in total knee arthroplasty (TKA) as an attempt to reduce polyethylene wear. However, the long-term survival of this component is not known. We performed a retrospective review of a prospectively collected database to assess the ten year survival and clinical and radiological outcomes of an oxidised zirconium total knee arthroplasty with the Genesis II prosthesis. The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Knee Injury and Osteoarthritis Outcome Score (KOOS) and a patient satisfaction scale were used to assess outcome. A total of 303 consecutive TKAs were performed in 278 patients with a mean age of 68 years (45 to 89). The rate of survival ten years post-operatively as assessed using Kaplan-Meier analysis was 97% (95% confidence interval 94 to 99) with revision for any reason as the endpoint. There were no revisions for loosening, osteolysis or failure of the implant. There was a significant improvement in all components of the WOMAC score at final follow-up (p < 0.001). The mean individual components of the KOOS score for symptoms (82.4 points; 36 to 100), pain (87.5 points; 6 to 100), activities of daily life (84.9 points; 15 to 100) and quality of life (71.4 points; 6 to 100) were all at higher end of the scale. This study provides further supportive evidence that the oxidised zirconium TKA gives comparable rates of survival with other implants and excellent functional outcomes ten years post-operatively. Total knee arthroplasty with an oxidised zirconium femoral component gives comparable long-term rates of survival and functional outcomes with conventional implants. ©2016 The British Editorial Society of Bone & Joint Surgery.

A three-enzyme cascade reaction through positional assembly of enzymes in a polymersome nanoreactor.

PubMed

van Dongen, Stijn F M; Nallani, Madhavan; Cornelissen, Jeroen J L M; Nolte, Roeland J M; van Hest, Jan C M

2009-01-01

Porous polymersomes based on block copolymers of isocyanopeptides and styrene have been used to anchor enzymes at three different locations, namely, in their lumen (glucose oxidase, GOx), in their bilayer membrane (Candida antarctica lipase B, CalB) and on their surface (horseradish peroxidase, HRP). The surface coupling was achieved by click chemistry between acetylene-functionalised anchors on the surface of the polymersomes and azido functions of HRP, which were introduced by using a direct diazo transfer reaction to lysine residues of the enzyme. To determine the encapsulation and conjugation efficiency of the enzymes, they were decorated with metal-ion labels and analysed by mass spectrometry. This revealed an almost quantitative immobilisation efficiency of HRP on the surface of the polymersomes and a more than statistical incorporation efficiency for CalB in the membrane and for GOx in the aqueous compartment. The enzyme-decorated polymersomes were studied as nanoreactors in which glucose acetate was converted by CalB to glucose, which was oxidised by GOx to gluconolactone in a second step. The hydrogen peroxide produced was used by HRP to oxidise 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) to ABTS(.+). Kinetic analysis revealed that the reaction step catalysed by HRP is the fastest in the cascade reaction.

Probing the effect of charge transfer enhancement in off resonance mode SERS via conjugation of the probe dye between silver nanoparticles and metal substrates.

PubMed

Selvakannan, Pr; Ramanathan, Rajesh; Plowman, Blake J; Sabri, Ylias M; Daima, Hemant K; O'Mullane, Anthony P; Bansal, Vipul; Bhargava, Suresh K

2013-08-21

The charge transfer-mediated surface enhanced Raman scattering (SERS) of crystal violet (CV) molecules that were chemically conjugated between partially polarized silver nanoparticles and optically smooth gold and silver substrates has been studied under off-resonant conditions. Tyrosine molecules were used as a reducing agent to convert silver ions into silver nanoparticles where oxidised tyrosine caps the silver nanoparticle surface with its semiquinone group. This binding through the quinone group facilitates charge transfer and results in partially oxidised silver. This establishes a chemical link between the silver nanoparticles and the CV molecules, where the positively charged central carbon of CV molecules can bind to the terminal carboxylate anion of the oxidised tyrosine molecules. After drop casting Ag nanoparticles bound with CV molecules it was found that the free terminal amine groups tend to bind with the underlying substrates. Significantly, only those CV molecules that were chemically conjugated between the partially polarised silver nanoparticles and the underlying gold or silver substrates were found to show SERS under off-resonant conditions. The importance of partial charge transfer at the nanoparticle/capping agent interface and the resultant conjugation of CV molecules to off resonant SERS effects was confirmed by using gold nanoparticles prepared in a similar manner. In this case the capping agent binds to the nanoparticle through the amine group which does not facilitate charge transfer from the gold nanoparticle and under these conditions SERS enhancement in the sandwich configuration was not observed.

Water structuring and collagen adsorption at hydrophilic and hydrophobic silicon surfaces.

PubMed

Cole, Daniel J; Payne, Mike C; Ciacchi, Lucio Colombi

2009-12-28

The adsorption of a collagen fragment on both a hydrophobic, hydrogen-terminated and a hydrophilic, natively oxidised Si surface is investigated using all-atom molecular dynamics. While favourable direct protein-surface interactions via localised contact points characterise adhesion to the hydrophilic surface, evenly spread surface/molecule contacts and stabilisation of the helical structure occurs upon adsorption on the hydrophobic surface. In the latter case, we find that adhesion is accompanied by a mutual fit between the hydrophilic/hydrophobic pattern within the protein and the layered water structure at the solid/liquid interface, which may provide an additional driving force to the classic hydrophobic effect.

Study of the activity of quaternary ammonium compounds in the mitigation of biofouling in heat exchangers-condensers cooled by seawater.

PubMed

Trueba, Alfredo; Otero, Félix M; González, José A; Vega, Luis M; García, Sergio

2013-01-01

The effectiveness of two quaternary ammonium compounds (QACs) (non-oxidising biocides) to reduce the growth of biofilm adhering to the tubes of a heat exchanger-condenser cooled by seawater was evaluated. Their effectiveness was compared to that of a conventional oxidising biocide (sodium hypochlorite [NaOCl]) under the same testing conditions. Each biocide was applied intermittently (6 h on, 6 h off) in a first shock stage (1.5 ppm over 8 days) and a second stabilising stage (0.5 ppm over 20 days). The results showed that the antifouling effectiveness of the first of the QACs (fifth generation) was comparable to that shown by the oxidising power of NaOCl. Although the reaction time was longer than that of NaOCl, both the compounds removed the biofilm, and the tube was practically restored to its clean condition. Treatment with the second of the QACs (fourth generation) allowed for the stabilisation of biofilm growth, but not for its removal. Ecotoxicology studies classified the QACs as environmentally harmless under the testing conditions.

As(III) oxidation by MnO2 during groundwater treatment.

PubMed

Gude, J C J; Rietveld, L C; van Halem, D

2017-03-15

The top layer of natural rapid sand filtration was found to effectively oxidise arsenite (As(III)) in groundwater treatment. However, the oxidation pathway has not yet been identified. The aim of this study was to investigate whether naturally formed manganese oxide (MnO 2 ), present on filter grains, could abiotically be responsible for As(III) oxidation in the top of a rapid sand filter. For this purpose As(III) oxidation with two MnO 2 containing powders was investigated in aerobic water containing manganese(II) (Mn(II)), iron(II) (Fe(II)) and/or iron(III) (Fe(III)). The first MnO 2 powder was a very pure - commercially available - natural MnO 2 powder. The second originated from a filter sand coating, produced over 22 years in a rapid filter during aeration and filtration. Jar test experiments showed that both powders oxidised As(III). However, when applying the MnO 2 in aerated, raw groundwater, As(III) removal was not enhanced compared to aeration alone. It was found that the presence of Fe(II)) and Mn(II) inhibited As(III) oxidation, as Fe(II) and Mn(II) adsorption and oxidation were preferred over As(III) on the MnO 2 surface (at pH 7). Therefore it is concluded that just because MnO 2 is present in a filter bed, it does not necessarily mean that MnO 2 will be available to oxidise As(III). However, unlike Fe(II), the addition of Fe(III) did not hinder As(III) oxidation on the MnO 2 surface; resulting in subsequent effective As(V) removal by the flocculating hydrous ferric oxides. Copyright © 2016 Elsevier Ltd. All rights reserved.

Surface Modification of Boron-Doped Diamond with Microcrystalline Copper Phthalocyanine: Oxygen Reduction Catalysis

PubMed Central

Gan, Patrick; Foord, John S; Compton, Richard G

2015-01-01

Surface modification of boron-doped diamond (BDD) with copper phthalocyanine was achieved using a simple and convenient dropcast deposition, giving rise to a microcrystalline structure. Both unmodified and modified BDD electrodes of different surface terminations (namely hydrogen and oxygen) were compared via the electrochemical reduction of oxygen in aqueous solution. A significant lowering of the cathodic overpotential by about 500 mV was observed after modification of hydrogen-terminated (hydrophobic) diamond, while no voltammetric peak was seen on modified oxidised (hydrophilic) diamond, signifying greater interaction between copper phthalocyanine and the hydrogen-terminated BDD. Oxygen reduction was found to undergo a two-electron process on the modified hydrogen-terminated diamond, which was shown to be also active for the reduction of hydrogen peroxide. The lack of a further conversion of the peroxide was attributed to its rapid diffusion away from the triple phase boundary at which the reaction is expected to exclusively occur. PMID:26491640

The membrane biofilm reactor: the natural partnership of membranes and biofilm.

PubMed

Rittmann, B E

2006-01-01

Many exciting new technologies for water-quality control combine microbiological processes with adsorption, advanced oxidation, a membrane or an electrode to improve performance, address emerging contaminants or capture renewable energy. An excellent example is the H2-based membrane biofilm reactor (MBfR), which delivers H2 gas to a biofilm that naturally accumulates on the outer surface of a bubbleless membrane. Autotrophic bacteria in the biofilm oxidise the H2 and use the electrons to reduce NO3-, CIO4- and other oxidised contaminants. This natural partnership of membranes and biofilm makes it possible to gain many cost, performance and simplicity advantages from using H2 as the electron donor for microbially catalysed reductions. The MBfR has been demonstrated for denitrification in drinking water; reduction of perchlorate in groundwater; reduction of selenate, chromate, trichloroethene and other emerging contaminants; advanced N removal in wastewater treatment and autotrophic total-N removal.

Structure of Thermobifida fusca DyP-type peroxidase and activity towards Kraft lignin and lignin model compounds.

PubMed

Rahmanpour, Rahman; Rea, Dean; Jamshidi, Shirin; Fülöp, Vilmos; Bugg, Timothy D H

2016-03-15

A Dyp-type peroxidase enzyme from thermophilic cellulose degrader Thermobifida fusca (TfuDyP) was investigated for catalytic ability towards lignin oxidation. TfuDyP was characterised kinetically against a range of phenolic substrates, and a compound I reaction intermediate was observed via pre-steady state kinetic analysis at λmax 404 nm. TfuDyP showed reactivity towards Kraft lignin, and was found to oxidise a β-aryl ether lignin model compound, forming an oxidised dimer. A crystal structure of TfuDyP was determined, to 1.8 Å resolution, which was found to contain a diatomic oxygen ligand bound to the heme centre, positioned close to active site residues Asp-203 and Arg-315. The structure contains two channels providing access to the heme cofactor for organic substrates and hydrogen peroxide. Site-directed mutant D203A showed no activity towards phenolic substrates, but reduced activity towards ABTS, while mutant R315Q showed no activity towards phenolic substrates, nor ABTS. Copyright © 2016 Elsevier Inc. All rights reserved.

Development of oxidised and heat-moisture treated potato starch film.

PubMed

Zavareze, Elessandra da Rosa; Pinto, Vânia Zanella; Klein, Bruna; El Halal, Shanise Lisie Mello; Elias, Moacir Cardoso; Prentice-Hernández, Carlos; Dias, Alvaro Renato Guerra

2012-05-01

This study investigated the effects of sodium hypochlorite oxidation and a heat-moisture treatment of potato starch on the physicochemical, pasting and textural properties of potato starches in addition to the water vapour permeability (WVP) and mechanical properties of potato starch films produced from these starches. The carbonyl contents, carboxyl contents, swelling power, solubility, pasting properties and gel texture of the native, oxidised and heat-moisture treated (HMT) starches were evaluated. The films made of native, oxidised and HMT starches were characterised by thickness, water solubility, colour, opacity, mechanical properties and WVP. The oxidised and HMT starches had lower viscosity and swelling power compared to the native starch. The films produced from oxidised potato starch had decreased solubility, elongation and WVP values in addition to increased tensile strength compared to the native starch films. The HMT starch increased the tensile strength and WVP of the starch films compared to the native starch. Copyright © 2011 Elsevier Ltd. All rights reserved.

Lupus high-density lipoprotein induces proinflammatory responses in macrophages by binding lectin-like oxidised low-density lipoprotein receptor 1 and failing to promote activating transcription factor 3 activity.

PubMed

Smith, Carolyne K; Seto, Nickie L; Vivekanandan-Giri, Anuradha; Yuan, Wenmin; Playford, Martin P; Manna, Zerai; Hasni, Sarfaraz A; Kuai, Rui; Mehta, Nehal N; Schwendeman, Anna; Pennathur, Subramaniam; Kaplan, Mariana J

2017-03-01

Recent evidence indicates that high-density lipoprotein (HDL) exerts vasculoprotective activities by promoting activating transcription factor 3 (ATF3), leading to downregulation of toll-like receptor (TLR)-induced inflammatory responses. Systemic lupus erythematosus (SLE) is associated with increased cardiovascular disease risk not explained by the Framingham risk score. Recent studies have indicated oxidised HDL as a possible contributor. We investigated the potential mechanisms by which lupus HDL may lose its anti-inflammatory effects and promote immune dysregulation. Control macrophages were challenged with control and SLE HDL in vitro and examined for inflammatory markers by real-time qRT-PCR, confocal microscopy, ELISA and flow cytometry. Lupus-prone mice were treated with an HDL mimetic (ETC-642) in vivo and inflammatory cytokine levels measured by real-time qRT-PCR and ELISA. Compared with control HDL, SLE HDL activates NFκB, promotes inflammatory cytokine production and fails to block TLR-induced inflammation in control macrophages. This failure of lupus HDL to block inflammatory responses is due to an impaired ability to promote ATF3 synthesis and nuclear translocation. This inflammation is dependent on lectin-like oxidised low-density lipoprotein receptor 1 (LOX1R) binding and rho-associated, coiled-coil containing protein kinase 1 and 2 (ROCK1/2) kinase activity. HDL mimetic-treated lupus mice showed significant ATF3 induction and proinflammatory cytokine abrogation. Lupus HDL promotes proinflammatory responses through NFκB activation and decreased ATF3 synthesis and activity in an LOX1R-dependent and ROCK1/2-dependent manner. HDL mimetics should be explored as potential therapies for inflammation and SLE cardiovascular risk. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

Spontaneous modification of carbon surface with neutral red from its diazonium salts for bioelectrochemical systems.

PubMed

Guo, Kun; Chen, Xin; Freguia, Stefano; Donose, Bogdan C

2013-09-15

This study introduces a novel and simple method to covalently graft neutral red (NR) onto carbon surfaces based on spontaneous reduction of in situ generated NR diazonium salts. Immobilization of neutral red on carbon surface was achieved by immersing carbon electrodes in NR-NaNO2-HCl solution. The functionalized electrodes were characterized by cyclic voltammetry (CV), atomic force microscope (AFM), and X-ray photoelectron spectroscopy (XPS). Results demonstrated that NR attached in this way retains high electrochemical activity and proved that NR was covalently bound to the carbon surface via the pathway of reduction of aryl diazonium salts. The NR-modified electrodes showed a good stability when stored in PBS solution in the dark. The current output of an acetate-oxidising microbial bioanode made of NR-modified graphite felts were 3.63±0.36 times higher than the unmodified electrodes, which indicates that covalently bound NR can act as electron transfer mediator to facilitate electron transfer from bacteria to electrodes. Copyright © 2013 Elsevier B.V. All rights reserved.

Evaluation of the use of moss transplants (Pseudoscleropodium purum) for biomonitoring different forms of air pollutant nitrogen compounds.

PubMed

Varela, Z; García-Seoane, R; Arróniz-Crespo, M; Carballeira, A; Fernández, J A; Aboal, J R

2016-06-01

We investigated whether three different types of moss transplants (devitalized moss bags with and without cover and auto-irrigated moss transplants) are suitable for use as biomonitors of the deposition of oxidised and/or reduced forms of N. For this purpose, we determined whether the concentration of atmospheric NO2 was related to the % N, δ(15)N and the activity of the enzyme biomarkers phosphomonoesterase (PME) and nitrate reductase (NR) in the tissues of moss transplants. We exposed the transplants in 5 different environments of Galicia (NW Spain) and Cataluña (NE Spain): industrial environments, urban and periurban environments, the surroundings of a cattle farm and in a monitoring site included in the sampling network of the European Monitoring Programme. The results showed that the moss in the auto-irrigated transplants was able of incorporating the N in its tissues because it was metabolically active, whereas in devitalized moss bags transplants, moss simply intercepts physically the N compounds that reached it in particulate or gaseous form. In addition, this devitalization could limit the capacity of moss to capture gaseous compounds (i.e. reduced N) and to reduce the oxidised compounds that reach the specimens. These findings indicate that devitalized moss transplants cannot be used to monitor either oxidised or reduced N compounds, whereas transplants of metabolically active moss can be used for this purpose. Finally, the NR and PME biomarkers should be used with caution because of the high variability in their activities and the limits of quantification should be evaluated in each case. Copyright © 2016 Elsevier Ltd. All rights reserved.

Intravitreal properties of porous silicon photonic crystals

PubMed Central

Cheng, L; Anglin, E; Cunin, F; Kim, D; Sailor, M J; Falkenstein, I; Tammewar, A; Freeman, W R

2009-01-01

Aim To determine the suitability of porous silicon photonic crystals for intraocular drug-delivery. Methods A rugate structure was electrochemically etched into a highly doped p-type silicon substrate to create a porous silicon film that was subsequently removed and ultrasonically fractured into particles. To stabilise the particles in aqueous media, the silicon particles were modified by surface alkylation (using thermal hydrosilylation) or by thermal oxidation. Unmodified particles, hydrosilylated particles and oxidised particles were injected into rabbit vitreous. The stability and toxicity of each type of particle were studied by indirect ophthalmoscopy, biomicroscopy, tonometry, electroretinography (ERG) and histology. Results No toxicity was observed with any type of the particles during a period of >4 months. Surface alkylation led to dramatically increased intravitreal stability and slow degradation. The estimated vitreous half-life increased from 1 week (fresh particles) to 5 weeks (oxidised particles) and to 16 weeks (hydrosilylated particles). Conclusion The porous silicon photonic crystals showed good biocompatibility and may be used as an intraocular drug-delivery system. The intravitreal injectable porous silicon photonic crystals may be engineered to host a variety of therapeutics and achieve controlled drug release over long periods of time to treat chronic vitreoretinal diseases. PMID:18441177

Estimation and influence of physicochemical properties and chemical fractions of surface sediment on the bioaccessibility of Cd and Hg contaminant in Langat River, Malaysia.

PubMed

Kadhum, Safaa A; Ishak, Mohd Yusoff; Zulkifli, Syaizwan Zahmir

2017-10-01

This study applied the use of sequential extraction technique and simple bioaccessibility extraction test to quantify the bioavailable fractions and the human bioaccessible concentration of metals collected from nine stations in surface sediment of the Langat River. The concentrations of total and bioaccessible metals from different stations were in the range of 0.49-1.04, 0.10-0.32 μg g -1 for T-Cd, Bio-Cd, respectively, and 12.9-128.03, 2.06-8.53 μg kg -1 for T-Hg, Bio-Hg, respectively. The results revealed highest R-Bio-Cd in Banting station (55.3 %), while the highest R-Bio-Hg was in Kajang station (49.61 %). The chemical speciation of Cd in most sampling stations was in the order of oxidisable-organic > residual > exchangeable > acid-reducible, while speciation of Hg was in the order of exchangeable > residual > oxidisable-organic > acid-reducible. The correlation matric of mean content showed that the TOM, particle size and Mg ++ in polluted surface sediments was highly correlated with total mercury. The PCA showed that the main factors influencing the bioaccessibility of Hg in surface sediments were the sediment TOM, F1 (EFLE) and F3 (oxidation-organic), while the factor influencing the bioaccessibility of Cd was the F3 (oxidation-organic) and T-Cd.

An a priori study of different tabulation methods for turbulent pulverised coal combustion

NASA Astrophysics Data System (ADS)

Luo, Yujuan; Wen, Xu; Wang, Haiou; Luo, Kun; Jin, Hanhui; Fan, Jianren

2018-05-01

In many practical pulverised coal combustion systems, different oxidiser streams exist, e.g. the primary- and secondary-air streams in the power plant boilers, which makes the modelling of these systems challenging. In this work, three tabulation methods for modelling pulverised coal combustion are evaluated through an a priori study. Pulverised coal flames stabilised in a three-dimensional turbulent counterflow, consisting of different oxidiser streams, are simulated with detailed chemistry first. Then, the thermo-chemical quantities calculated with different tabulation methods are compared to those from detailed chemistry solutions. The comparison shows that the conventional two-stream flamelet model with a fixed oxidiser temperature cannot predict the flame temperature correctly. The conventional two-stream flamelet model is then modified to set the oxidiser temperature equal to the fuel temperature, both of which are varied in the flamelets. By this means, the variations of oxidiser temperature can be considered. It is found that this modified tabulation method performs very well on prediction of the flame temperature. The third tabulation method is an extended three-stream flamelet model that was initially proposed for gaseous combustion. The results show that the reference gaseous temperature profile can be overall reproduced by the extended three-stream flamelet model. Interestingly, it is found that the predictions of major species mass fractions are not sensitive to the oxidiser temperature boundary conditions for the flamelet equations in the a priori analyses.

The use of an oxidising mouthwash to reduce staining associated with chlorhexidine. Studies in vitro and in vivo.

PubMed

Addy, M; al-Arrayed, F; Moran, J

1991-04-01

Discolouration of the teeth, tongue and dental restorative materials associated with the use of cationic antiseptics is still the limiting factor in long-term usage of antiplaque agents such as chlorhexidine. Oxidising agents have been used successfully to remove dental stain in animals, but products and regimens have not been evaluated in humans. These pilot studies in vitro and in vivo assessed a long-established oxidising mouthwash, based on peroxyborate, for stain removal from teeth and acrylic. The laboratory studies measured chlorhexidine tea stain removal from tooth and acrylic specimens. The oxidising agent markedly reduced staining on specimens. In a short-term clinical experiment, dental staining was forced over a 2 1/2-day period by reciprocal chlorhexidine and tea rinsing. 5 rinses with the oxidising mouthwash during the next 1 1/2 days dramatically reduced staining compared with water after rinses. Additionally, a single rinse with peroxyborate following the 5 water after rinses, again considerably reduced the residual staining. Effects on tongue staining were less impressive. Both experimental models produced findings consistent with those from the animal model. The results suggest proprietary oxidising mouthwashes could have a place in the control of dental stain associated with the use of chlorhexidine. Further studies to evaluate such products in a more conventional chlorhexidine regimen are indicated.

Absence of residual structure in the intrinsically disordered regulatory protein CP12 in its reduced state

DOE Office of Scientific and Technical Information (OSTI.GOV)

Launay, Hélène; Barré, Patrick; Puppo, Carine

2016-08-12

The redox switch protein CP12 is a key player of the regulation of the Benson–Calvin cycle. Its oxidation state is controlled by the formation/dissociation of two intramolecular disulphide bridges during the day/night cycle. CP12 was known to be globally intrinsically disordered on a large scale in its reduced state, while being partly ordered in the oxidised state. By combining Nuclear Magnetic Resonance and Small Angle X-ray Scattering experiments, we showed that, contrary to secondary structure or disorder predictions, reduced CP12 is fully disordered, with no transient or local residual structure likely to be precursor of the structures identified in themore » oxidised active state and/or in the bound state with GAPDH or PRK. These results highlight the diversity of the mechanisms of regulation of conditionally disordered redox switches, and question the stability of oxidised CP12 scaffold. - Highlights: • CP12 is predicted to form two helices in its N-terminal sequence. • Reduced CP12 is disordered as a random coil according to SAXS. • Limited or no transient structures are observed in reduced CP12 by NMR.« less

Antioxidants inhibit low density lipoprotein oxidation less at lysosomal pH: A possible explanation as to why the clinical trials of antioxidants might have failed.

PubMed

Ahmad, Feroz; Leake, David S

2018-03-05

Oxidised low density lipoprotein (LDL) was considered to be important in the pathogenesis of atherosclerosis, but the large clinical trials of antioxidants, including the first one using probucol (the PQRST Trial), failed to show benefit and have cast doubt on the importance of oxidised LDL. We have shown previously that LDL oxidation can be catalysed by iron in the lysosomes of macrophages. The aim of this study was therefore to investigate the effectiveness of antioxidants in preventing LDL oxidation at lysosomal pH and also establish the possible mechanism of oxidation. Probucol did not effectively inhibit the oxidation of LDL at lysosomal pH, as measured by conjugated dienes or oxidised cholesteryl esters or tryptophan residues in isolated LDL or by ceroid formation in the lysosomes of macrophage-like cells, in marked contrast to its highly effective inhibition of LDL oxidation at pH 7.4. LDL oxidation at lysosomal pH was inhibited very effectively for long periods by N,N'-diphenyl-1,4-phenylenediamine, which is more hydrophobic than probucol and has been shown by others to inhibit atherosclerosis in rabbits, and by cysteamine, which is a hydrophilic antioxidant that accumulates in lysosomes. Iron-induced LDL oxidation might be due to the formation of the superoxide radical, which protonates at lysosomal pH to form the much more reactive, hydrophobic hydroperoxyl radical, which can enter LDL and reach its core. Probucol resides mainly in the surface monolayer of LDL and would not effectively scavenge hydroperoxyl radicals in the core of LDL. This might explain why probucol failed to protect against atherosclerosis in various clinical trials. The oxidised LDL hypothesis of atherosclerosis now needs to be re-evaluated using different and more effective antioxidants that protect against the lysosomal oxidation of LDL. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

Behaviour of human endothelial cells on surface modified NiTi alloy.

PubMed

Plant, Stuart D; Grant, David M; Leach, Lopa

2005-09-01

Intravascular stents are being designed which utilise the shape memory properties of NiTi alloy. Despite the clinical advantages afforded by these stents their application has been limited by concerns about the large nickel ion content of the alloy. In this study, the surface chemistry of NiTi alloy was modified by mechanical polishing and oxidising heat treatments and subsequently characterised using X-ray photon spectroscopy (XPS). The effect of these surfaces on monolayer formation and barrier integrity of human umbilical vein endothelial cells (HUVEC) was then assessed by confocal imaging of the adherens junctional molecule VE-cadherin, perijunctional actin and permeability to 42kDa dextrans. Dichlorofluoroscein assays were used to measure oxidative stress in the cells. XPS analysis of NiTi revealed its surface to be dominated by TiO(2). However, where oxidation had occurred after mechanical polishing or post polishing heat treatments at 300 and 400 degrees C in air, a significant amount of metallic nickel or nickel oxide species (10.5 and 18.5 at%) remained on the surface. Exposure of HUVECs to these surfaces resulted in increased oxidative stress within the cells, loss of VE-cadherin and F-actin and significantly increased paracellular permeability. These pathological phenomena were not found in cells grown on NiTi which had undergone heat treatment at 600 degrees C. At this temperature thickening of the TiO(2) layer had occurred due to diffusion of titanium ions from the bulk of the alloy, displacing nickel ions to sub-surface areas. This resulted in a significant reduction in nickel ions detectable on the sample surface (4.8 at%). This study proposes that the integrity of human endothelial monolayers on NiTi is dependent upon the surface chemistry of the alloy and that this can be manipulated, using simple oxidising heat treatments.

Nanoscale in-depth modification of CrOSi layers

NASA Astrophysics Data System (ADS)

Bertóti, I.; Tóth, A.; Mohai, M.; Kelly, R.; Marletta, G.; Farkas-Jahnke, M.

1997-02-01

In-depth modification of CrOSi layers on a nanoscale has been performed by low energy inert (Ar +, He +) and reactive (N 2+) ions. Chemical and short range structural investigations were done by XPS. Cr and Si were essentially oxidised in the as-prepared (i.e. virgin) samples. Ar + bombardment led to a nearly complete reduction of Cr to Cr 0. At the same time, about one third of the oxidised Si was converted to Si 0, which was shown to form SiCr bonds. Also, silicide type clusters, predicted earlier by XPS, have been identified by glancing angle electron diffraction. He + bombardment led to an increase of the surface O concentration. This was manifested also in the disruption of SiCr bonds formed by the preceding Ar + bombardment and conversion of Cr and Si predominantly to Cr 3+O, Cr 6+O and Si 4+O. With N 2+ bombardment formation of CrN and SiN bonds was observed. The thickness of the transformed surface layers were about 5 nm, 9 nm and 30 nm for Ar, N and He projectiles as estimated by TRIM calculations. The observed transformations were interpreted in terms of the relative importance of sputtering or ion induced mixing for Ar + and He +, and also by the role of thermodynamic driving forces.

Mineralogy and evolution of the surface of Mars: A review

NASA Astrophysics Data System (ADS)

Chevrier, V.; Mathé, P. E.

2007-02-01

We review the mineralogy of the surface of Mars, using data from various sources, including in situ characterisations performed by landers, remote observations from orbit, and studies of the SNC meteorites. We also discuss the possible alteration processes and the factor controlling them, and try to relate the mineralogical observations to the chemical evolution of the surface materials on Mars in order to identify the dominant process(es). Then we try to describe a possible chemical and mineralogical evolution of the surface materials, resulting from weathering driven by the abundance and activity of water. Even if weathering is the dominant process responsible for the surface evolution, all observations suggest that it is strongly affected locally in time and space by various other processes including hydrothermalism, volcanism, evaporites, meteoritic impacts and aeolian erosion. Nevertheless, the observed phases on the surface of Mars globally depend on the evolution of the weathering conditions. This hypothesis, if confirmed, could give a new view of the evolution of the martian surface, roughly in three steps. The first would correspond to clay-type weathering process in the Noachian, under a probable thick H 2O/CO 2-rich atmosphere. Then, during the Hesperian when water became scarcer and its activity sporadic, linked to volcanic activity, sulfate-type acidic weathering process would have been predominant. The third period would be like today, a very slow weathering by strongly oxidising agents (H 2O 2, O 2) in cold and dry conditions, through solid-gas or solid-films of water resulting frost-thaw and/or acid fog. This would favour poorly crystalline phases, mainly iron (oxy) hydroxides. But in this scenario many questions remain about the transition between these processes, and about the factors affecting the evolution of the weathering process.

Effects of geodynamic setting on the redox state of fluids released by subducted mantle lithosphere

NASA Astrophysics Data System (ADS)

Evans, K. A.; Reddy, S. M.; Tomkins, A. G.; Crossley, R. J.; Frost, B. R.

2017-05-01

Magnetite breakdown during subduction of serpentinised ultramafic rocks may produce oxidised fluids that oxidise the deep Earth and/or the sub-arc mantle, either via direct transport of ferric iron, or via redox reactions between ferric iron and other elements, such as sulfur. However, so far, there is no consensus on the oxidation state of fluids released during subduction of ultramafic rocks, or the factors that control this oxidation state. Subducted samples from a magma-poor rifted margin and a supra-subduction zone geodynamic setting were compared to examine evidence of changes in opaque phase assemblage and ferric iron content as a consequence of subduction, and as a function of geodynamic setting. Thermodynamic calculations in the system Fe-Ni-O-H-S and Fe-Ni-O-S at the pressures and temperatures of interest were used to constrain oxygen activities and fluid compositions. Samples from New Caledonia, which exemplify supra-subduction zone mantle, contain awaruite (FeNi3) and equilibrated with hydrogen-bearing fluids at oxygen activity less than the FMQ (fayalite-magnetite-quartz) buffer. In contrast, samples from the Zermatt Saas Zone ophiolite, Western Alps, which are thought to represent mantle from a subducted magma-poor rifted margin, contain magnetite plus sulfur-rich phases such as pyrite (FeS2), and are inferred to have equilibrated with hydrogen-poor fluids at oxygen activity greater than FMQ. This major difference is independent of differences in subduction pressure-temperature conditions, variation in peridotite protolith composition, or the nature of adjacent units. We propose that the Zermatt Saas Zone samples would have undergone more complete serpentinisation prior to subduction than the supra-subduction zone (SSZ) New Caledonian samples. This difference explains the different fluid compositions, because incompletely serpentinised rocks containing olivine and brucite retain or evolve awaruite-bearing assemblages that buffer fluid compositions to high hydrogen activity (aH2). Ultramafic rocks are associated with two distinctly different fluid compositions during pre-subduction and subduction serpentinisation. Initially, while olivine is in equilibrium with infiltrating fluid, mineral assemblages that include awaruite in the rocks buffer fluids to H2-bearing, low aO2 compositions. Deserpentinisation of incompletely serpentinised rocks in which awaruite is present also produces H2-bearing fluids. Once awaruite is exhausted, H2-poor, high aO2 fluids co-exist with awaruite-absent assemblages, and deserpentinisation of such rocks would produce H2O-rich fluids. Thus, deserpentinisation of ultramafic rocks could produce either hydrogen-bearing fluids that could infiltrate and reduce the sub-arc mantle, or more oxidised fluids, which could transfer redox budget to other geochemical reservoirs such as the sub-arc mantle. Therefore, the redox contribution of subducted ultramafic rocks to the deep Earth and sub-arc mantle depends on the extent of protolith serpentinisation. Pre-subduction settings that promote extensive serpentinisation by oxidised fluids at high fluid:rock ratios in open systems, such as slow and ultraslow spreading ridges, transform faults, oceanic core complexes, and exhumed mantle at rifted continental margins, may produce more oxidised fluids than those associated with less pervasive serpentinisation and fluids that may be rock-buffered to a reduced state.

Microbial oxidation of arsenite in a subarctic environment: diversity of arsenite oxidase genes and identification of a psychrotolerant arsenite oxidiser

USGS Publications Warehouse

Osborne, Thomas H.; Jamieson, Heather E.; Hudson-Edwards, Karen A.; Nordstrom, D. Kirk; Walker, Stephen R.; Ward, Seamus A.; Santini, Joanne M.

2010-01-01

Background: Arsenic is toxic to most living cells. The two soluble inorganic forms of arsenic are arsenite (+3) and arsenate (+5), with arsenite the more toxic. Prokaryotic metabolism of arsenic has been reported in both thermal and moderate environments and has been shown to be involved in the redox cycling of arsenic. No arsenic metabolism (either dissimilatory arsenate reduction or arsenite oxidation) has ever been reported in cold environments (i.e. < 10°C).Results: Our study site is located 512 kilometres south of the Arctic Circle in the Northwest Territories, Canada in an inactive gold mine which contains mine waste water in excess of 50 mM arsenic. Several thousand tonnes of arsenic trioxide dust are stored in underground chambers and microbial biofilms grow on the chamber walls below seepage points rich in arsenite-containing solutions. We compared the arsenite oxidisers in two subsamples (which differed in arsenite concentration) collected from one biofilm. 'Species' (sequence) richness did not differ between subsamples, but the relative importance of the three identifiable clades did. An arsenite-oxidising bacterium (designated GM1) was isolated, and was shown to oxidise arsenite in the early exponential growth phase and to grow at a broad range of temperatures (4-25°C). Its arsenite oxidase was constitutively expressed and functioned over a broad temperature range.Conclusions: The diversity of arsenite oxidisers does not significantly differ from two subsamples of a microbial biofilm that vary in arsenite concentrations. GM1 is the first psychrotolerant arsenite oxidiser to be isolated with the ability to grow below 10°C. This ability to grow at low temperatures could be harnessed for arsenic bioremediation in moderate to cold climates.

Oxidised zirconium versus cobalt alloy bearing surfaces in total knee arthroplasty: 3D laser scanning of retrieved polyethylene inserts.

PubMed

Anderson, F L; Koch, C N; Elpers, M E; Wright, T M; Haas, S B; Heyse, T J

2017-06-01

We sought to establish whether an oxidised zirconium (OxZr) femoral component causes less loss of polyethylene volume than a cobalt alloy (CoCr) femoral component in total knee arthroplasty. A total of 20 retrieved tibial inserts that had articulated with OxZr components were matched with 20 inserts from CoCr articulations for patient age, body mass index, length of implantation, and revision diagnosis. Changes in dimensions of the articular surfaces were compared with those of pristine inserts using laser scanning. The differences in volume between the retrieved and pristine surfaces of the two groups were calculated and compared. The loss of polyethylene volume was 122 mm 3 (standard deviation (sd) 87) in the OxZr group and 170 mm 3 (sd 96) in the CoCr group (p = 0.033). The volume loss in the OxZr group was also lower in the medial (72 mm 3 (sd 67) versus 92 mm 3 (sd 60); p = 0.096) and lateral (49 mm 3 (sd 36) versus 79 mm 3 (sd 61); p = 0.096) compartments separately, but these differences were not significant. Our results corroborate earlier findings from in vitro testing and visual retrieval analysis which suggest that polyethylene volume loss is lower with OxZr femoral components. Since both OxZr and CoCr are hard surfaces that would be expected to create comparable amounts of polyethylene creep, the differences in volume loss may reflect differences in the in vivo wear of these inserts. Cite this article: Bone Joint J 2017;99-B:793-8. ©2017 The British Editorial Society of Bone & Joint Surgery.

Antioxidant properties of 3-deoxyanthocyanidins and polyphenolic extracts from Côte d'Ivoire's red and white sorghums assessed by ORAC and in vitro LDL oxidisability tests.

PubMed

Carbonneau, Marie-Annette; Cisse, Moctar; Mora-Soumille, Nathalie; Dairi, Sofiane; Rosa, Maxence; Michel, Françoise; Lauret, Céline; Cristol, Jean-Paul; Dangles, Olivier

2014-02-15

Red sorghum is a source of phenolic compounds (PCs), including 3-deoxyanthocyanidins that may protect against oxidative stress related disease such as atherosclerosis. HPLC was used to characterise and quantify PCs extracted from red or white sorghum whole grain flour. Antioxidant activity was measured by an oxygen radical absorbance capacity assay and against LDL-oxidisability, and further compared to that of synthesised 3-deoxyanthocyanidins (i.e., luteolinidin and apigeninidin). Phenolic content of red and white sorghums was evaluated as 3.90 ± 0.01 and 0.07 ± 0.01 mmol gallic acid equivalents L(-1), respectively. Luteolinidin and apigeninidin were mainly found in red sorghum. Red sorghum had almost 3 and 10 times greater specific antioxidant activity compared to luteolinidin and apigeninidin, respectively. Red sorghum PCs and the two 3-deoxyanthocyanidins were also effective at preventing LDL vitamin E depletion and conjugated diene production. Red sorghum flour exhibits antioxidant capacity suggesting that it may be a valuable health-promoting food. Copyright © 2013 Elsevier Ltd. All rights reserved.

Synthesis and properties of dithymidine phosphate analogues containing 3'-thiothymidine.

PubMed Central

Cosstick, R; Vyle, J S

1990-01-01

Dithymidine-3'-S-phosphorothioate (d(TspT)) has been prepared from a 5'-O-monomethoxytritylthymidine-3'-S-phosphorothioamidite (7) by activation with 5-(p-nitrophenyl)tetrazole in the presence of 3'-O-acetylthymidine. The resulting dinucleoside phosphorothioite is readily oxidised to the corresponding 3'-S-phosphorothioate using either tetrabutylammonium (TBA) periodate or TBA oxone and has been deprotected under standard conditions to yield d(TspT). This dithymidine phosphate analogue is comparatively resistant to hydrolysis by nuclease P1, but the P-S bond is readily cleaved by aqueous solutions of either iodine or silver nitrate. Dithymidine-3'-S-phosphorodithioate (d[Tsp(s)T]) was prepared in an analogous fashion using sulphur to oxidise the intermediate dinucleoside phosphorothioite. Absolute stereochemistry has been assigned to the diastereoisomers of d[Tsp(s)T] by comparing their physical and chemical properties to those of the dinucleoside phosphorothioates. PMID:2315041

Fatigue Testing of AA7050-T7451 with Various Corrosion Prevention Surface Treatments

DTIC Science & Technology

2013-06-01

UNCLASSIFIED Authors Marcus McDonald Air Vehicles Division Marcus McDonald initially spent 3 years working in the oil & gas, steel and...treatments: caustic degreasing, de-oxidising or anodising. The pits in the anodised coupons were larger than the pits caused by the pre-IVD etching...those fatigue cracks that grew from them spent less time in growing whilst they were small, because the crack started at what was a larger effective

Chemical state and distribution of iodine deposits on 17% Cr/12% Ni steel oxidised in CO 2/CH 3I gas mixtures

NASA Astrophysics Data System (ADS)

Allen, G. C.; Tyler, J. W.

1990-03-01

Iodine-131 is one of the most important volatile fission product elements with respect to radiobiological impact, and the characterisation of its chemical state and distribution on reactor surfaces is required for reactor safety assessments. To this end, duplicate samples of Type 316 (17%Cr/12% Ni) stainless steel oxidised in {CO 2}/{CH 3}I gas mixtures and previously characterised using X-ray photoelectron spectroscopy have been examined using Raman spectroscopy. The aim is to improve our understanding of the way in which iodine is distributed throughout the oxide scale and to identify its chemical state. In this paper we present Raman spectra recorded from a series of stainless steel specimens together with spectra recorded from a number of standard iodine compounds. It is demonstrated that the technique is well suited as a fingerprint method of species identification, can differentiate between the chemical state of iodine as iodide and iodate and can analyse thin oxide films (5-50 nm). Identification of iodine deposits in these oxide films at concentrations of ⩽ 2 at% was not achieved however, there being insufficient iodine present to distinguish any peaks present from the background signal. It is concluded that local concentrations of iodine in oxide inclusions of different composition/morphology on the steel surface does not occur to any extent.

Potential nitrification and denitrification and the corresponding composition of the bacterial communities in a compact constructed wetland treating landfill leachates.

PubMed

Sundberg, C; Tonderski, K; Lindgren, P E

2007-01-01

Constructed wetlands can be used to decrease the high ammonium concentrations in landfill leachates. We investigated nitrification/denitrification activity and the corresponding bacterial communities in landfill leachate that was treated in a compact constructed wetland, Tveta Recycling Facility, Sweden. Samples were collected at three depths in a filter bed and the sediment from a connected open pond in July, September and November 2004. Potential ammonia oxidation was measured by short-term incubation method and potential denitrification by the acetylene inhibition technique. The ammonia-oxidising and the denitrifying bacterial communities were investigated using group-specific PCR primers targeting 16S rRNA genes and the functional gene nosZ, respectively. PCR products were analysed by denaturing gradient gel electrophoresis and nucleotide sequencing. The same degree of nitrification activity was observed in the pond sediment and at all levels in the filter bed, whereas the denitrification activity decreased with filter bed depth. Denitrification rates were higher in the open pond, even though the denitrifying bacterial community was more diverse in the filter bed. The ammonia-oxidising community was also more varied in the filter bed. In the filter bed and the open pond, there was no obvious relationship between the nitrification/denitrification activities and the composition of the corresponding bacterial communities.

New Passivation Methods of GaAs.

DTIC Science & Technology

1980-01-01

Fabrication of Thin Nitride Layers on GaAs 33 - 35 CHAPTER 7 Passivation of InGaAsP 36 - 37 CHAPTER 8 Emulsions on GaAs Surfaces 38 - 42 APPENDIX...not yet given any useful results. The deposition of SiO2 by using emulsions is pursued and first results on the possibility of GaAs doping are...glycol-tartaric acid based aqueous solution was used in order to anodically oxidise the gate notch after the source and drain ohmic contacts were formed

Investigation of boundary conditions for biomimetic HA deposition on titanium oxide surfaces.

PubMed

Lindgren, M; Astrand, M; Wiklund, U; Engqvist, H

2009-07-01

To improve the clinical outcome of metal implants, i.e. earlier loading and reduction of the incidence of revision surgery, better bone bonding ability is wanted. One method to achieve this is to change the surface chemistry to give a surface that facilitates bone bonding in vivo, i.e. a bioactive surface. Crystalline titanium oxide has recently been proven to be bioactive in vitro and is an interesting option to the more common hydroxylapatite (HA) coatings on implants. A materials possible in vitro bioactivity is tested through soaking in simulated body fluid and studies of possible HA formation on the surface. For bioactive materials, the formed HA layer can also be used as a coating. The aim of the current paper is to investigate some boundary conditions for HA formation on crystalline titanium oxide surfaces regarding influence from coating thickness, soaking time and soaking temperature. The influence from soaking time and temperature on the HA growth were investigated on oxidised Ti samples, (24 h at 800 degrees C) resulting in a rutile surface structure. The oxidised samples were tested at three temperatures (4, 37 and 65 degrees C) and four times (1 h, 1 day, 1 week and 4 weeks). The influence from titanium coating thickness on the HA growth was investigated via depositing thin films of crystalline titanium dioxide on Ti plates using a reactive magnetron sputtering process. Four different PVD runs with coating thicknesses between 19 and 74 nm were tested. The soaking temperature had an effect on the HA formation and growth on both rutile surfaces and native oxide on Ti substrates. Higher temperatures lead to easier formation of HA. It was even possible, at 65 degrees C, to grow HA on native titanium oxide from soaking in PBS. The coating quality was better for HA formed at 65 degrees C compared to 37 degrees C. All PVD-coatings showed HA growth after 1 week in PBS at 37 degrees C, thus even very thin coatings of crystalline titanium oxide coatings are bioactive.

Life in the dark: metagenomic evidence that a microbial slime community is driven by inorganic nitrogen metabolism.

PubMed

Tetu, Sasha G; Breakwell, Katy; Elbourne, Liam D H; Holmes, Andrew J; Gillings, Michael R; Paulsen, Ian T

2013-06-01

Beneath Australia's large, dry Nullarbor Plain lies an extensive underwater cave system, where dense microbial communities known as 'slime curtains' are found. These communities exist in isolation from photosynthetically derived carbon and are presumed to be chemoautotrophic. Earlier work found high levels of nitrite and nitrate in the cave waters and a high relative abundance of Nitrospirae in bacterial 16S rRNA clone libraries. This suggested that these communities may be supported by nitrite oxidation, however, details of the inorganic nitrogen cycling in these communities remained unclear. Here we report analysis of 16S rRNA amplicon and metagenomic sequence data from the Weebubbie cave slime curtain community. The microbial community is comprised of a diverse assortment of bacterial and archaeal genera, including an abundant population of Thaumarchaeota. Sufficient thaumarchaeotal sequence was recovered to enable a partial genome sequence to be assembled, which showed considerable synteny with the corresponding regions in the genome of the autotrophic ammonia oxidiser Nitrosopumilus maritimus SCM1. This partial genome sequence, contained regions with high sequence identity to the ammonia mono-oxygenase operon and carbon fixing 3-hydroxypropionate/4-hydroxybutyrate cycle genes of N. maritimus SCM1. Additionally, the community, as a whole, included genes encoding key enzymes for inorganic nitrogen transformations, including nitrification and denitrification. We propose that the Weebubbie slime curtain community represents a distinctive microbial ecosystem, in which primary productivity is due to the combined activity of archaeal ammonia-oxidisers and bacterial nitrite oxidisers.

Evaluation of hybrid processes for nitrification by comparing MBBR/AS and IFAS configurations.

PubMed

Germain, E; Bancroft, L; Dawson, A; Hinrichs, C; Fricker, L; Pearce, P

2007-01-01

An integrated fixed-film activated sludge (IFAS) pilot plant and a moving bed biofilm reactor coupled with an activated sludge process (MBBR/AS) were operated under different temperatures, carbon loadings and solids retention times (SRTs). These two types of hybrid systems were compared, focusing on the nitrification capacity and the nitrifiers population of the media and suspended biomass alongside other process performances such as carbonaceous and total nitrogen (TN) removal rates. At high temperatures and loadings rates, both processes were fully nitrifying and achieved similarly high carbonaceous removal rates. However, under these conditions, the IFAS configuration performed better in terms of TN removal. Lower temperatures and carbon loadings led to lower carbonaceous removal rates for the MBBR/AS configuration, whereas the IFAS configuration was not affected. However, the nitrification capacity of the IFAS process decreased significantly under these conditions and the MBBR/AS process was more robust in terms of nitrification. Ammonia oxidising bacteria (AOB) and nitrite oxidising bacteria (NOB) population counts accurately reflected the changes in nitrification capacity. However, significantly less NOBs than AOBs were observed, without noticeable nitrite accumulation, suggesting that the characterisation method used was not as sensitive for NOBs and/or that the NOBs had a higher activity than the AOBs.

Sulphur bacteria mediated formation of Palaeoproterozoic phosphorites

NASA Astrophysics Data System (ADS)

Joosu, Lauri; Lepland, Aivo; Kirsimäe, Kalle

2014-05-01

Modern phosphorite formation is typically associated with high productivity in upwelling areas where apatite (Ca-phosphate) precipitation is mediated by sulphur oxidising bacteria [1]. They inhabit the oxic/anoxic interface within the upper few centimetres of sediment column, accumulating phosphate in their cells under oxic conditions and releasing it rapidly when conditions become anoxic. Sulphur bacteria are known to live in close association with a consortium of anaerobic methane oxidising archaea and syntrophic sulphate-reducing bacteria. Paleoproterozoic, c. 2.0 Ga Zaonega Formation in Karelia, Russia contains several P-rich intervals in the upper part of 1500 m thick succession of organic-rich sedimentary rocks interlayered with mafic tuffs and lavas. Apatite in these P-rich intervals forms impure laminae, lenses and round-oval nodules which diameters typically range from 300 to 1000 μm. Individual apatite particles in P-rich laminae and nodules commonly occur as cylinders that are 1-8 μm long and have diameters of 0.5-4 μm. Cross-sections of best preserved cylindrical apatite particles reveal a thin outer rim whereas the internal parts consist of small anhedral elongated crystallites, intergrown with carbonaceous material. During recrystallization the outer rim thickens towards interior and cylinders may attain hexagonal crystal habit, but their size and shape remains largely unchanged [2]. The sizes of Zaonega nodules are similar to giant sulphide-oxidising bacteria known from modern and ancient settings [3, 4]. Individual apatite cylinders and aggregates have shapes and sizes similar to the methanotrophic archaea that inhabit microbial mats in modern seep/vent areas where they operate in close associations with sulphur-oxidising microbial communities [5]. Seep/vent influence during the Zaonega phosphogenesis is indicated by variable, though positive Eu anomaly, expected in magmatically active sedimentary environment experiencing several lava flows. Moreover, P-rich intervals in the Zaonega Formation are found in organic-rich sediments exhibiting strongly negative δ13Corg values (-37 to -34 per mil) which is interpreted to reflect the methanotrophic biomass. We conclude that modern-style phosphogenesis, mediated by sulphide-oxidising bacteria living in consortium with methanotrophs, was established at least 2 Ga ago. [1] Schulz and Schulz (2005) Science 307, 416-418 [2] Lepland, Joosu, Kirsimäe, Prave, Romashkin, Črne, Martin, Fallick, Somelar, Üpraus, Mänd, Roberts, van Zuilen, Wirth, Schreiber (2014) Nature geoscience 7, 20-24 [3] Bailey, Joye, Kalanetra, Flood, and Corsetti (2007) Nature 445, 198-201 [4] Schulz, Brinkhoff, Ferdelman, Marine, Teske and Jorgensen (1999) Science 284, 493-495 [5] Knittel, Losekann, Boetius, Kort and Amann (2005) Applied and Environmental Microbiology 71, 467-479.

Enhanced ethylene photodegradation performance of g-C3N4-Ag3PO4 composites with direct Z-scheme configuration.

PubMed

Chen, Xuxing; Huang, Xintang; Yi, Zhiguo

2014-12-22

Photocatalytic oxidation of ethylene continues to be a challenge at the frontier of chemistry. In a previous report, a simple Ag3 PO4 semiconductor material was shown to have strong photooxidative properties and efficiently oxidised water and decomposed organics in aqueous solution under visible-light illumination. Herein, its effects on the photo-oxidation of gaseous C2 H4 were investigated by fabricating graphitic C3 N4-Ag3 PO4 composite semiconductors with direct Z-scheme configuration. It was found that both the ethylene photo-oxidative activity and the stability of Ag3 PO4 are considerably improved by fabrication of Z-scheme composites. Moreover, stable C2 H4 photo-oxidation activity could be obtained by treating the composite at 450 °C for 3 h after long-term operation. From the point of view of environmental pollutant cleanup, the present technique avoids the side reaction of oxidising water and will be valuable for further investigations on both Ag3 PO4 and CH degradation. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Analysis of a Microbial Community in the UV/O3-Anaerobic/Aerobic Integrated Process for Petrochemical Nanofiltration Concentrate (NFC) Treatment by 454-Pyrosequencing.

PubMed

Wei, Chao; He, Wenjie; Wei, Li; Li, Chunying; Ma, Jun

2015-01-01

In this study, high-throughput pyrosequencing was applied on the analysis of the microbial community of activated sludge and biofilm in a lab-scale UV/O3- anaerobic/aerobic (A/O) integrated process for the treatment of petrochemical nanofiltration concentrate (NFC) wastewater. NFC is a type of saline wastewater with low biodegradability. From the anaerobic activated sludge (Sample A) and aerobic biofilm (Sample O), 59,748 and 51,231 valid sequence reads were obtained, respectively. The dominant phylotypes related to the metabolism of organic compounds, polycyclic aromatic hydrocarbon (PAH) biodegradation, assimilation of carbon from benzene, and the biodegradation of nitrogenous organic compounds were detected as genus Clostridium, genera Pseudomonas and Stenotrophomonas, class Betaproteobacteria, and genus Hyphomicrobium. Furthermore, the nitrite-oxidising bacteria Nitrospira, nitrite-reducing and sulphate-oxidising bacteria (NR-SRB) Thioalkalivibrio were also detected. In the last twenty operational days, the total Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) removal efficiencies on average were 64.93% and 62.06%, respectively. The removal efficiencies of ammonia nitrogen and Total Nitrogen (TN) on average were 90.51% and 75.11% during the entire treatment process.

The Analysis of a Microbial Community in the UV/O3-Anaerobic/Aerobic Integrated Process for Petrochemical Nanofiltration Concentrate (NFC) Treatment by 454-Pyrosequencing

PubMed Central

Wei, Chao; He, Wenjie; Wei, Li; Li, Chunying; Ma, Jun

2015-01-01

In this study, high-throughput pyrosequencing was applied on the analysis of the microbial community of activated sludge and biofilm in a lab-scale UV/O3- anaerobic/aerobic (A/O) integrated process for the treatment of petrochemical nanofiltration concentrate (NFC) wastewater. NFC is a type of saline wastewater with low biodegradability. From the anaerobic activated sludge (Sample A) and aerobic biofilm (Sample O), 59,748 and 51,231 valid sequence reads were obtained, respectively. The dominant phylotypes related to the metabolism of organic compounds, polycyclic aromatic hydrocarbon (PAH) biodegradation, assimilation of carbon from benzene, and the biodegradation of nitrogenous organic compounds were detected as genus Clostridium, genera Pseudomonas and Stenotrophomonas, class Betaproteobacteria, and genus Hyphomicrobium. Furthermore, the nitrite-oxidising bacteria Nitrospira, nitrite-reducing and sulphate-oxidising bacteria (NR-SRB) Thioalkalivibrio were also detected. In the last twenty operational days, the total Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) removal efficiencies on average were 64.93% and 62.06%, respectively. The removal efficiencies of ammonia nitrogen and Total Nitrogen (TN) on average were 90.51% and 75.11% during the entire treatment process. PMID:26461260

IV INTERNATIONAL CONFERENCE ON ATOM AND MOLECULAR PULSED LASERS (AMPL'99): Surface oxide removal by a XeCl laser for decontamination

NASA Astrophysics Data System (ADS)

Sentis, M. L.; Delaporte, Ph; Marine, W.; Uteza, O.

2000-06-01

The laser ablation performed with an automated excimer XeCl laser unit is used for large surface cleaning. The study focuses on metal surfaces that are oxidised and are representative of contaminated surfaces with radionuclides in a context of nuclear power plant maintenance. The unit contains an XeCl laser, the beam delivery system, the particle collection cell, and the system for real-time control of cleaning processes. The interaction of laser radiation with a surface is considered, in particular, the surface damage caused by cleaning radiation. The beam delivery system consists of an optical fibre bundle of 5 m long and allows delivering 150 W at 308 nm for laser surface cleaning. The cleaning process is controlled by analysing in real time the plasma electric field evolution. The system permits the cleaning of 2 to 6 m2 h-1 of oxides with only slight substrate modifications.

Oxidation of anthracene using waste Mn oxide minerals: the importance of wetting and drying sequences.

PubMed

Clarke, Catherine; Tourney, Janette; Johnson, Karen

2012-02-29

PAHs are a common problem in contaminated urban soils due to their recalcitrance. This study presents results on the oxidation of anthracene on synthetic and natural Mn oxide surfaces. Evaporation of anthracene spiked Mn oxide slurries in air results in the oxidation of 30% of the anthracene to anthraquinone. Control minerals, quartz and calcite, also oxidised a small but significant proportion of the anthracene (4.5% and 14% conversion, respectively) when spiked mineral slurries were evaporated in air. However, only Mn oxide minerals showed significant anthracene oxidation (5-10%) when evaporation took place in the absence of oxygen (N2 atmosphere). In the fully hydrated systems where no drying took place, natural Mn oxides showed an increase in anthracene oxidation with decreasing pH, with a conversion of 75% anthracene at pH 4. These results show both acidification and drying favor the oxidation of anthracene on Mn oxide mineral surfaces. It has also been demonstrated that non-redox active mineral surfaces, such as calcite, may play a role in contaminant breakdown during wetting and drying sequences. Given that climate changes suggest that wetting and drying sequences are likely to become more significant these results have important implications for contaminated land remediation technologies. Copyright © 2012 Elsevier B.V. All rights reserved.

Thiamine losses during storage of pasteurised and sterilized model systems of minced chicken meat with addition of fresh and oxidized fat, and antioxidants.

PubMed

Szymandera-Buszka, Krystyna; Hęś, Marzanna; Waszkowiak, Katarzyna; Jędrusek-Golińska, Anna

2014-01-01

The aim of the study was to determine the effect of pasteurisation and sterilization of model systems of minced chicken meat in the presence of low or high-oxidised pork lard, soy and sunflower oil, as well as casein hydrolysate and rosemary extract, on losses of thiamine in model systems. In the samples, the thiamine content was analysed periodically by thiochromium method, as well as rate of lipid oxidation based on measurement of peroxide value (PV) by iodometric method and p-anisidine value (AV) by spectrophotometric method. It was observed that the thiamine losses in model systems of minced chicken after pasteurisation (61-71%) were higher than after sterilization (57-67%). Introduction of high-oxidised fat increased the total thiamine losses both during thermal processing and storage of meat samples (to 23%). A strong relationship was established between thiamine losses and rate of fat oxidation. The lowest total thiamine losses were observed in the samples with low-oxidised pork lard. Antioxidant addition (rosemary extract or casein hydrolysate) into meat samples limited the thiamine losses. However, the effect depended on oxidation of fat that was mixed with meat. In the samples with low-oxidised fat, higher protective effect was found for rosemary extract (7-11%). In the samples with high-oxidised fat, casein hydrolysate was superior to rosemary extract (14%). In order to increase the stability of thiamine in pasteurized or sterilized meat products with fats, the influence of fat type and its oxidative stability should be taken under consideration. Moreover, the addition of rosemary extract or casein hydrolysate has impact on the thiamine losses since it slows down lipid oxidation to a significant extent.

Electrochemical Detection of the Molecules of Life

NASA Technical Reports Server (NTRS)

Thomson, Seamus; Quinn, Richard; Koehne, Jessica

2017-01-01

All forms of life on Earth contain cellular machinery that can transform and regulate chemical energy through metabolic pathways. These processes are oxidation-reduction reactions that are performed by four key classes of molecules: flavins, nicotinamaides, porphyrins, and quinones. By detecting the electrochemical interaction of these redox-active molecules with an electrode, a method of differentiating them by their class could be established and incorporated into future life-detecting missions. This body of work investigates the electrochemistry of ubiquitous molecules found in life and how they may be detected. Molecules can oxidise or reduce the surface of an electrode - giving or receiving electrons - and these interactions are represented by changes in current with respect to an applied voltage. This relationship varies with: electrolyte type and concentration, working electrode material, the redox-active molecule itself, and scan rate. Flavin adenine dinucleotide (FAD), riboflavin, nicotinamide adenine dinucleotide (NADH), and anthraquinone are all molecules found intracellularly in almost all living organisms. An organism-synthesised extracellular redox-active molecule, Plumbagin, was also selected as part of this study. The goal of this work is to detect these molecules in seawater and assess its application in searching for life on Ocean Worlds.

Differential nitric oxide synthesis and host apoptotic events correlate with bleaching susceptibility in reef corals

NASA Astrophysics Data System (ADS)

Hawkins, T. D.; Krueger, T.; Becker, S.; Fisher, P. L.; Davy, S. K.

2014-03-01

Coral bleaching poses a threat to coral reefs worldwide. As a consequence of the temperature-induced breakdown in coral-dinoflagellate symbiosis, bleaching can have extensive effects on reef communities. However, our understanding of bleaching at a cellular level is limited, and this is particularly true regarding differential susceptibility among coral species. Recent work suggests that bleaching may represent a host innate immune-like response to symbiont dysfunction that involves synthesis of the signalling compound nitric oxide (NO) and the induction of host apoptotic-like cell death. In this study, we examined the activity of apoptosis-regulating enzymes alongside oxidised NO accumulation (a proxy for NO synthesis) in the reef corals Acropora millepora, Montipora digitata, and Pocillopora damicornis during experimental thermal stress. P. damicornis was the most sensitive species, suffering mortality (tissue sloughing) after 5 days at 33 °C but non-lethal bleaching after 9 days at 31.5 °C. A. millepora bleached at 33 °C but remained structurally intact, while M. digitata showed little evidence of bleaching. P. damicornis and A. millepora both exhibited evidence of temperature-induced NO synthesis and, after 5 days of heating, levels of oxidised NO in both species were fivefold higher than in controls maintained at 28.5 °C. These responses preceded bleaching by a number of days and may have occurred before symbiont dysfunction (measured as chlorophyll a degradation and oxidised NO accumulation). In A. millepora, apparent NO synthesis correlated with the induction of host apoptotic-like pathways, while in P. damicornis, the upregulation of apoptotic pathways occurred later. No evidence of elevated NO production or apoptosis was observed in M. digitata at 33 °C and baseline activity of apoptosis-regulating enzymes was negligible in this species. These findings provide important physiological data in the context of the responses of corals to global change and suggest that early events in the host may be important in the collapse of the coral-dinoflagellate symbiosis.

Study of the formation of thermochemical laser-induced periodic surface structures on Cr, Ti, Ni and NiCr films under femtosecond irradiation

NASA Astrophysics Data System (ADS)

Dostovalov, A. V.; Korolkov, V. P.; Terentyev, V. S.; Okotrub, K. A.; Dultsev, F. N.; Babin, S. A.

2017-07-01

The formation of femtosecond laser-induced periodic surface structures (LIPSS's) on Cr, Ti, Ni and NiCr films (with different Cr contents) is investigated. It is established that thermochemical LIPSS's with periods of 950, 930 and 980 nm are formed, respectively, on the surfaces of titanium, chromium, and nichrome (with a chromium content of 20%); however, thermochemical LIPSS's are not formed on the surfaces of nickel and nichrome with a low chromium content, although Raman data indicate that oxidation occurs in all cases. A weakly ordered ablated structure with a period of 250-300 nm is found to be formed on oxidised areas of thermochemical LIPSS's in the case of chromium and nichrome (80/20). Experimental data on selective etching of thermochemical LIPSS's on titanium and chromium films are presented.

Possible ecological risk of two pharmaceuticals diclofenac and paracetamol demonstrated on a model plant Lemna minor.

PubMed

Kummerová, Marie; Zezulka, Štěpán; Babula, Petr; Tříska, Jan

2016-01-25

Lemna minor is often used in environmental risk assessment and it can be supposed that usually evaluated parameters will be reliable even for assessing the risk of pharmaceuticals. Subtle changes in duckweed plant number, biomass production, and leaf area size induced by 10-day-exposure to diclofenac (DCF) and paracetamol (PCT) (0.1, 10, and 100 μg/L), excepting 100 μg/L DCF, are in contrast with considerable changes on biochemical and histochemical level. Both drugs caused a decrease in content of photosynthetic pigments (by up to 50%), an increase in non-photochemical quenching (by 65%) and decrease in relative chlorophyll fluorescence decay values (by up to 90% with DCF). Both DCF and especially PCT increased amount of reactive nitrogen and oxygen species in roots. DCF-induced effects included mainly increased lipid peroxidation (by 78%), disturbation in membrane integrity and lowering both oxidoreductase and dehydrogenase activities (by 30%). PCT increased the content of soluble proteins and phenolics. Higher concentrations of both DCF and PCT increased the levels of oxidised ascorbate (by 30%) and oxidised thiols (by up to 84% with DCF). Glutathion-reductase activity was elevated by both pharmaceuticals (nearly by 90%), glutathion-S-transferase activity increased mainly with PCT (by 22%). The early and sensitive indicators of DCF and PCT phytotoxicity stress in duckweed are mainly the changes in biochemical processes, connected with activation of defense mechanisms against oxidative stress. Copyright © 2015 Elsevier B.V. All rights reserved.

A Review of Green Strategies to Prevent or Mitigate Microbiologically Influenced Corrosion

DTIC Science & Technology

2007-01-01

microbiologically influenced corrosion (MIC) has may provide nutrients for regrowth. been to use oxidising (e.g. chlorine, bromine, ozone ) Videla et al...MPN method: 6cells/cm2 Total bacteria Figure 6. Number of bacteria in biofilm using two detection techniques : fluorescent antibody (FA) and most...nitrite, lation of nitrate- utilising bacteria in the system. nitrous oxide or nitrogen and oxidising sulfide to Hubert et al. (2006) suggested that

Spatially resolved variations in reflectivity across iron oxide thin films

NASA Astrophysics Data System (ADS)

Kelley, Chris S.; Thompson, Sarah M.; Gilks, Daniel; Sizeland, James; Lari, Leonardo; Lazarov, Vlado K.; Matsuzaki, Kosuke; LeFrançois, Stéphane; Cinque, Gianfelice; Dumas, Paul

2017-11-01

The spin polarising properties of the iron oxide magnetite (Fe3O4) make it attractive for use in spintronic devices, but its sensitivity to compositional and structural variations make it challenging to prepare reliably. Infrared microspectroscopy and modelling are used to determine the spatial variation in the chemical composition of three thin films of iron oxide; one prepared by pulsed laser deposition (PLD), one by molecular beam epitaxy (MBE) deposition of iron whilst simultaneously flowing oxygen into the chamber and one by flowing oxygen only once deposition is complete. The technique is easily able to distinguish between films which contain metallic iron and different iron oxide phases as well as spatial variations in composition across the films. The film grown by post-oxidising iron is spatially uniform but not fully oxidised, the film grown by simultaneously oxidising iron showed spatial variation in oxide composition while the film grown by PLD was spatially uniform magnetite.

Graphitic and oxidised high pressure high temperature (HPHT) nanodiamonds induce differential biological responses in breast cancer cell lines.

PubMed

Woodhams, Benjamin; Ansel-Bollepalli, Laura; Surmacki, Jakub; Knowles, Helena; Maggini, Laura; de Volder, Michael; Atatüre, Mete; Bohndiek, Sarah

2018-06-19

Nanodiamonds have demonstrated potential as powerful sensors in biomedicine, however, their translation into routine use requires a comprehensive understanding of their effect on the biological system being interrogated. Under normal fabrication processes, nanodiamonds are produced with a graphitic carbon shell, but are often oxidized in order to modify their surface chemistry for targeting to specific cellular compartments. Here, we assessed the biological impact of this purification process, considering cellular proliferation, uptake, and oxidative stress for graphitic and oxidized nanodiamond surfaces. We show for the first time that oxidized nanodiamonds possess improved biocompatibility compared to graphitic nanodiamonds in breast cancer cell lines, with graphitic nanodiamonds inducing higher levels of oxidative stress despite lower uptake.

Ammonia oxidisers in a non-nitrifying Brazilian savanna soil.

PubMed

Catão, Elisa C P; Thion, Cécile; Krüger, R H; Prosser, James I

2017-11-01

Low nitrification rates in Brazilian savanna (Cerrado) soils have puzzled researchers for decades. Potential mechanisms include biological inhibitors, low pH, low microbial abundance and low soil moisture content, which hinders microbial activity, including ammonia oxidation. Two approaches were used to evaluate these potential mechanisms: (i) manipulation of soil moisture and pH in microcosms containing Cerrado soil and (ii) assessment of nitrification inhibition in slurries containing mixtures of Cerrado soil and an actively nitrifying agricultural soil. Despite high ammonium concentration in Cerrado soil microcosms, little NO3- accumulation was observed with increasing moisture or pH, but in some Cerrado soil slurries, ammonia-oxidising archaea (AOA) amoA transcripts were detected after 14 days. In mixed soil slurries, the final NO3- concentration reflected the initial proportions of agricultural and Cerrado soils in the mixture, providing no evidence of nitrification inhibitors in Cerrado soil. AOA community denaturing gradient gel electrophoresis profiles were similar in the mixed and nitrifying soils. These results suggest that nitrification in Cerrado soils is not constrained by water availability, ammonium availability, low pH or biological inhibitors, and alternative potential explanations for low nitrification levels are discussed. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

The active transport of histidine and its role in ATP production in Trypanosoma cruzi.

PubMed

Barisón, M J; Damasceno, F S; Mantilla, B S; Silber, A M

2016-08-01

Trypanosoma cruzi, the aetiological agent of Chagas's disease, metabolizes glucose, and after its exhaustion, degrades amino acids as energy source. Here, we investigate histidine uptake and its participation in energy metabolism. No putative genes for the histidine biosynthetic pathway have been identified in genome databases of T. cruzi, suggesting that its uptake from extracellular medium is a requirement for the viability of the parasite. From this assumption, we characterized the uptake of histidine in T. cruzi, showing that this amino acid is incorporated through a single and saturable active system. We also show that histidine can be completely oxidised to CO2. This finding, together with the fact that genes encoding the putative enzymes for the histidine - glutamate degradation pathway were annotated, led us to infer its participation in the energy metabolism of the parasite. Here, we show that His is capable of restoring cell viability after long-term starvation. We confirm that as an energy source, His provides electrons to the electron transport chain, maintaining mitochondrial inner membrane potential and O2 consumption in a very efficient manner. Additionally, ATP biosynthesis from oxidative phosphorylation was found when His was the only oxidisable metabolite present, showing that this amino acid is involved in bioenergetics and parasite persistence within its invertebrate host.

Green synthesis of silver nanoparticles using Terminalia chebula extract at room temperature and their antimicrobial studies

NASA Astrophysics Data System (ADS)

Mohan Kumar, Kesarla; Sinha, Madhulika; Mandal, Badal Kumar; Ghosh, Asit Ranjan; Siva Kumar, Koppala; Sreedhara Reddy, Pamanji

2012-06-01

A green rapid biogenic synthesis of silver nanoparticles (Ag NPs) using Terminalia chebula (T. chebula) aqueous extract was demonstrated in this present study. The formation of silver nanoparticles was confirmed by Surface Plasmon Resonance (SPR) at 452 nm using UV-visible spectrophotometer. The reduction of silver ions to silver nanoparticles by T. chebula extract was completed within 20 min which was evidenced potentiometrically. Synthesised nanoparticles were characterised using UV-vis spectroscopy, Fourier transformed infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and atomic force microscopy (AFM). The hydrolysable tannins such as di/tri-galloyl-glucose present in the extract were hydrolyzed to gallic acid and glucose that served as reductant while oxidised polyphenols acted as stabilizers. In addition, it showed good antimicrobial activity towards both Gram-positive bacteria (S. aureus ATCC 25923) and Gram-negative bacteria (E. coli ATCC 25922). Industrially it may be a smart option for the preparation of silver nanoparticles.

Assessment of DNA damage using comet assay in middle-aged overweight/obese subjects after following a hypocaloric diet supplemented with cocoa extract.

PubMed

Ibero-Baraibar, Idoia; Azqueta, Amaya; Lopez de Cerain, Adela; Martinez, J Alfredo; Zulet, M Angeles

2015-01-01

Nutrient excess and unbalanced diets can result in overproduction of reactive oxygen species (ROS), which are associated with oxidative stress. Cocoa extract contains antioxidants that inhibit the harmful effects of ROS. This trial analysed the effect of cocoa extract consumption integrated as a bioactive compound into ready-to-eat meals, on oxidative stress at the level of DNA in overweight/obese subjects. Fifty volunteers [57.26(5.24) years, 30.59(2.33)kg/m(2)] participated in a 4-week double-blind, randomised, placebo-controlled parallel nutritional intervention. Half of the volunteers received meals supplemented with 1.4 g/day cocoa extract, while the other half received control meals, both within a 15% energy restriction diet. Lymphocytes were isolated and endogenous strand breaks, oxidised bases and resistance to H2O2-induced damage were measured by the comet assay. The intake of ready-to-eat meals supplemented with cocoa extract did not show relevant changes in the oxidative status of DNA. However, in the cocoa group, oxidised bases negatively correlated with methyl epicatechin-O-sulphate (r = -0.76; P = -0.007) and epicatechin sulphate (r = -0.61; P = -0.046). When volunteers of both groups were analysed together, a marginal decrease (P = 0.072) in oxidised bases was observed, which attributed to weight loss. Subjects who started the intervention with higher levels of damage showed a greater reduction in oxidised bases after 4 weeks (P = 0.040) compared to those who had lower baseline levels. In conclusion, even if 1.4 g of cocoa supplementation for 4 weeks did not show notable changes in terms of antioxidant status of DNA, the energy restriction showed a slightly decrease in oxidised bases and this was seen to a greater extent in subjects who started the intervention with higher levels of damage. On the other hand, the inverse associations found between oxidised bases and some cocoa-derived metabolites suggest that a protective effect might be seen in a longer period of time or in subjects with higher baseline DNA damage. www.clinicaltrials.gov (NCT01596309). © The Author 2014. Published by Oxford University Press on behalf of the Mutagenesis Society. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Structural evidence for a copper-bound carbonate intermediate in the peroxidase and dismutase activities of superoxide dismutase.

PubMed

Strange, Richard W; Hough, Michael A; Antonyuk, Svetlana V; Hasnain, S Samar

2012-01-01

Copper-zinc superoxide dismutase (SOD) is of fundamental importance to our understanding of oxidative damage. Its primary function is catalysing the dismutation of superoxide to O(2) and H(2)O(2). SOD also reacts with H(2)O(2), leading to the formation of a strong copper-bound oxidant species that can either inactivate the enzyme or oxidise other substrates. In the presence of bicarbonate (or CO(2)) and H(2)O(2), this peroxidase activity is enhanced and produces the carbonate radical. This freely diffusible reactive oxygen species is proposed as the agent for oxidation of large substrates that are too bulky to enter the active site. Here, we provide direct structural evidence, from a 2.15 Å resolution crystal structure, of (bi)carbonate captured at the active site of reduced SOD, consistent with the view that a bound carbonate intermediate could be formed, producing a diffusible carbonate radical upon reoxidation of copper. The bound carbonate blocks direct access of substrates to Cu(I), suggesting that an adjunct to the accepted mechanism of SOD catalysed dismutation of superoxide operates, with Cu(I) oxidation by superoxide being driven via a proton-coupled electron transfer mechanism involving the bound carbonate rather than the solvent. Carbonate is captured in a different site when SOD is oxidised, being located in the active site channel adjacent to the catalytically important Arg143. This is the probable route of diffusion from the active site following reoxidation of the copper. In this position, the carbonate is poised for re-entry into the active site and binding to the reduced copper.

Structural Evidence for a Copper-Bound Carbonate Intermediate in the Peroxidase and Dismutase Activities of Superoxide Dismutase

PubMed Central

Strange, Richard W.; Hough, Michael A.; Antonyuk, Svetlana V.; Hasnain, S. Samar

2012-01-01

Copper-zinc superoxide dismutase (SOD) is of fundamental importance to our understanding of oxidative damage. Its primary function is catalysing the dismutation of superoxide to O2 and H2O2. SOD also reacts with H2O2, leading to the formation of a strong copper-bound oxidant species that can either inactivate the enzyme or oxidise other substrates. In the presence of bicarbonate (or CO2) and H2O2, this peroxidase activity is enhanced and produces the carbonate radical. This freely diffusible reactive oxygen species is proposed as the agent for oxidation of large substrates that are too bulky to enter the active site. Here, we provide direct structural evidence, from a 2.15 Å resolution crystal structure, of (bi)carbonate captured at the active site of reduced SOD, consistent with the view that a bound carbonate intermediate could be formed, producing a diffusible carbonate radical upon reoxidation of copper. The bound carbonate blocks direct access of substrates to Cu(I), suggesting that an adjunct to the accepted mechanism of SOD catalysed dismutation of superoxide operates, with Cu(I) oxidation by superoxide being driven via a proton-coupled electron transfer mechanism involving the bound carbonate rather than the solvent. Carbonate is captured in a different site when SOD is oxidised, being located in the active site channel adjacent to the catalytically important Arg143. This is the probable route of diffusion from the active site following reoxidation of the copper. In this position, the carbonate is poised for re-entry into the active site and binding to the reduced copper. PMID:22984565

High resolution and dynamic imaging of biopersistence and bioreactivity of extra and intracellular MWNTs exposed to microglial cells

PubMed Central

Gonzalez Carter, Daniel A.; Motskin, Michael; Pienaar, Ilse S.; Chen, Shu; Hu, Sheng; Ruenraroengsak, Pakatip; Ryan, Mary P.; Shaffer, Milo S. P.; Dexter, David T.

2016-01-01

Multi-walled carbon nanotubes (MWNTs) are increasingly being developed both as neuro-therapeutic drug delivery systems to the brain and as neural scaffolds to drive tissue regeneration across lesion sites. MWNTs with different degrees of acid oxidation may have different bioreactivities and propensities to aggregate in the extracellular environment, and both individualised and aggregated MWNTs may be expected to be found in the brain. Before practical application, it is vital to understand how both aggregates and individual MWNTs will interact with local phagocytic immune cells, the microglia, and ultimately to determine their biopersistence in the brain. The processing of extra- and intracellular MWNTs (both pristine and when acid oxidised) by microglia was characterised across multiple length scales by correlating a range of dynamic, quantitative and multi-scale techniques, including: UV-vis spectroscopy, light microscopy, focussed ion beam scanning electron microscopy and transmission electron microscopy. Dynamic, live cell imaging revealed the ability of microglia to break apart and internalise micron-sized extracellular agglomerates of acid oxidised MWNT, but not pristine MWNTs. The total amount of MWNTs internalised by, or strongly bound to, microglia was quantified as a function of time. Neither the significant uptake of oxidised MWNTs, nor the incomplete uptake of pristine MWNTs affected microglial viability, pro-inflammatory cytokine release or nitric oxide production. However, after 24 hrs exposure to pristine MWNTs, a significant increase in the production of reactive oxygen species was observed. Small aggregates and individualised oxidised MWNTs were present in the cytoplasm and vesicles, including within multilaminar bodies, after 72 hours. Some evidence of morphological damage to oxidised MWNT structure was observed including highly disordered graphitic structures, suggesting possible biodegradation. This work demonstrates the utility of dynamic, quantitative and multi-scale techniques in understanding the different cellular processing routes of functionalised nanomaterials. This correlative approach has wide implications for assessing the biopersistence of MWNT aggregates elsewhere in the body, in particular their interaction with macrophages in the lung. PMID:26298523

Manganese oxide mineralogy in an exhalative environment from the Solomon Islands

NASA Astrophysics Data System (ADS)

Taylor, G. R.

1983-04-01

The mineralogy and chemistry of oxidate facies sediments associated with a Solomon Island cupriferous pyrite deposit are described. Systematic variations in sediment composition are consistent with the gradual imposition of an oxidising environment on a pool of exhaled solution lying in a topographic depression on the sea floor. Manganese is first precipitated in the Mn2+ oxidation state as pyrochroite, γMn(OH)2. With later seafloor weathering and diagenesis, this oxidises initially to the Mn3+ intermediate minerals manganite (γMnO.OH) or, in the presence of iron hydroxides, to groutite (αMnO.OH). Subsequently, these oxidise further to Mn4+ as the βMnO2 dimorphs pyrolusite or ramsdellite, respectively. Todorokite (δMnO2) is indicative of more oxidising conditions and is found in the upper horizons of the manganiferous sediment. It is invariably non-stoichiometric in composition and its Mn2+/Mn4+ ratio is a direct function of the Eh prevailing during its precipitation. Adsorption of Na+, K+, Ca2+ and Ba2+ions at the time of formation stabilises the todorokite structure and provides an explanation for its persistence (with its Mn2+ions) in association with the completely oxidised Mn4+ mineral, βMnO2, pyrolusite. The enrichment of Cu, Zn and Pb in manganiferous sediments from both pelagic and exhalative environments is associated with the occurrence of goethite. The enrichment of K, Ba and Ca in manganiferous sediments from a similar range in environments is associated with the occurrence of todorokite. Both the mineralogy and trace element characteristics of a manganiferous sediment are thus a function of the environment of deposition rather than the ultimate source of the metals concerned. The trace element contents of manganiferous “floaters” should therefore only be used as an indicator of related sulphide mineralisation in the presence of other favourable factors.

Titan's Radioactive Haze : Production and Fate of Radiocarbon On Titan

NASA Astrophysics Data System (ADS)

Lorenz, R. D.; Jull, A. J. T.; Swindle, T. D.; Lunine, J. I.

Just as cosmic rays interact with nitrogen atoms in the atmosphere of Earth to gener- ate radiocarbon (14C), the same process should occur in Titan`s nitrogen-rich atmo- sphere. Titan`s atmosphere is thick enough that cosmic ray flux, rather than nitrogen column depth, limits the production of 14 C. Absence of a strong magnetic field and the increased distance from the sun suggest production rates of 9 atom/cm2/s, approx- imately 4 times higher than Earth. On Earth the carbon is rapidly oxidised into CO2. The fate and detectability of 14C on Titan depends on the chemical species into which it is incorporated in Titan's reducing atmosphere : as methane it would be hopelessly diluted even in only the atmosphere (ignoring the other, much more massive carbon reservoirs likely to be present on Titan, like hydrocarbon lakes.) However, in the more likely case that the 14C attaches to the haze that rains out onto the surface (as tholin, HCN or acetylene and their polymers - a much smaller carbon reservoir) , haze in the atmosphere or recently deposited on the surface would therefore be quite intrinsically radioactive. Such activity may modify the haze electrical charging and hence its coag- ulation. Measurements with compact instrumentation on future in-situ missions could place useful constraints on the mass deposition rates of photochemical material on the surface and identify locations where surface deposits of such material are `freshest`.

Study of porous silicon optical waveguides impregnated with organic dyes

NASA Astrophysics Data System (ADS)

Pirasteh, P.; Charrier, J.; Dumeige, Y.; Chaillou, A.; Guendouz, M.; Haji, L.

2007-01-01

Planar waveguides were made using oxidised porous silicon layers. Then, they were impregnated with Congo Red or Disperse Red 1 dyes. Optical losses were investigated before and after impregnation. In our case, the losses of impregnated waveguides were always higher than those of non-impregnated ones. In order to achieve a better understanding of the origin of these losses, we not only studied the absorbance of solutions which would impregnate the porous layers but also the reflectance spectra of the obtained composite materials. According to the measurements, the increase in losses in the visible spectrum depends on the intrinsic absorption of the dye while in NIR, the increase would be due to an accumulation of dried dye on the surface of the waveguide which would give rise to the surface scattering losses.

Archaea produce lower yields of N2 O than bacteria during aerobic ammonia oxidation in soil.

PubMed

Hink, Linda; Nicol, Graeme W; Prosser, James I

2017-12-01

Nitrogen fertilisation of agricultural soil contributes significantly to emissions of the potent greenhouse gas nitrous oxide (N 2 O), which is generated during denitrification and, in oxic soils, mainly by ammonia oxidisers. Although laboratory cultures of ammonia oxidising bacteria (AOB) and archaea (AOA) produce N 2 O, their relative activities in soil are unknown. This work tested the hypothesis that AOB dominate ammonia oxidation and N 2 O production under conditions of high inorganic ammonia (NH 3 ) input, but result mainly from the activity of AOA when NH 3 is derived from mineralisation. 1-octyne, a recently discovered inhibitor of AOB, was used to distinguish N 2 O production resulting from archaeal and bacterial ammonia oxidation in soil microcosms, and specifically inhibited AOB growth, activity and N 2 O production. In unamended soils, ammonia oxidation and N 2 O production were lower and resulted mainly from ammonia oxidation by AOA. The AOA N 2 O yield relative to nitrite produced was half that of AOB, likely due to additional enzymatic mechanisms in the latter, but ammonia oxidation and N 2 O production were directly linked in all treatments. Relative contributions of AOA and AOB to N 2 O production, therefore, reflect their respective contributions to ammonia oxidation. These results suggest potential mitigation strategies for N 2 O emissions from fertilised agricultural soils. © 2016 The Authors. Environmental Microbiology published by Society for Applied Microbiology and John Wiley & Sons Ltd.

A bio-anodic filter facilitated entrapment, decomposition and in situ oxidation of algal biomass in wastewater effluent.

PubMed

Mohammadi Khalfbadam, Hassan; Cheng, Ka Yu; Sarukkalige, Ranjan; Kaksonen, Anna H; Kayaalp, Ahmet S; Ginige, Maneesha P

2016-09-01

This study examined for the first time the use of bioelectrochemical systems (BES) to entrap, decompose and oxidise fresh algal biomass from an algae-laden effluent. The experimental process consisted of a photobioreactor for a continuous production of the algal-laden effluent, and a two-chamber BES equipped with anodic graphite granules and carbon-felt to physically remove and oxidise algal biomass from the influent. Results showed that the BES filter could retain ca. 90% of the suspended solids (SS) loaded. A coulombic efficiency (CE) of 36.6% (based on particulate chemical oxygen demand (PCOD) removed) was achieved, which was consistent with the highest CEs of BES studies (operated in microbial fuel cell mode (MFC)) that included additional pre-treatment steps for algae hydrolysis. Overall, this study suggests that a filter type BES anode can effectively entrap, decompose and in situ oxidise algae without the need for a separate pre-treatment step. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effect of mineral elements on physicochemical properties of oxidised starches and generation of free radicals.

PubMed

Pietrzyk, Sławomir; Fortuna, Teresa; Królikowska, Karolina; Rogozińska, Ewelina; Labanowska, Maria; Kurdziel, Magdalena

2013-09-12

The objective of this study was to determine the effect of enrichment of oxidised starches with mineral compounds on their physicochemical properties and capability for free radical generation. Potato and spelt wheat starches were oxidised with sodium hypochlorite and, afterwards, modified with ions of potassium, magnesium and iron. The modified starches were analysed for: content of mineral elements, colour parameters (L*a*b*), water binding capacity solubility in water at temperature of 50 and 80 °C, and susceptibility to enzymatic hydrolysis with α-amylase. In addition, thermodynamic characteristics of gelatinisation was determined by differential scanning calorimetry (DSC), and the number and character of thermally generated free radicals was assayed using electron paramagnetic resonance (EPR). Based on the results achieved, it was concluded that the quantity of incorporated minerals and changes in the assayed physicochemical parameters depended not only on the botanical type of starch but also on the type of the incorporated mineral element. Copyright © 2013 Elsevier Ltd. All rights reserved.

Ammonia concentration determines differential growth of ammonia-oxidising archaea and bacteria in soil microcosms.

PubMed

Verhamme, Daniel T; Prosser, James I; Nicol, Graeme W

2011-06-01

The first step of nitrification, oxidation of ammonia to nitrite, is performed by both ammonia-oxidising archaea (AOA) and ammonia-oxidising bacteria (AOB) in soil, but their relative contributions to ammonia oxidation and existence in distinct ecological niches remain to be determined. To determine whether available ammonia concentration has a differential effect on AOA and AOB growth, soil microcosms were incubated for 28 days with ammonium at three concentrations: native (control), intermediate (20 μg NH(4)(+)-N per gram of soil) and high (200 μg NH(4)(+)-N per gram of soil). Quantitative PCR demonstrated growth of AOA at all concentrations, whereas AOB growth was prominent only at the highest concentration. Similarly, denaturing gradient gel electrophoresis (DGGE) analysis revealed changes in AOA communities at all ammonium concentrations, whereas AOB communities changed significantly only at the highest ammonium concentration. These results provide evidence that ammonia concentration contributes to the definition of distinct ecological niches of AOA and AOB in soil.

Ammonia concentration determines differential growth of ammonia-oxidising archaea and bacteria in soil microcosms

PubMed Central

Verhamme, Daniel T; Prosser, James I; Nicol, Graeme W

2011-01-01

The first step of nitrification, oxidation of ammonia to nitrite, is performed by both ammonia-oxidising archaea (AOA) and ammonia-oxidising bacteria (AOB) in soil, but their relative contributions to ammonia oxidation and existence in distinct ecological niches remain to be determined. To determine whether available ammonia concentration has a differential effect on AOA and AOB growth, soil microcosms were incubated for 28 days with ammonium at three concentrations: native (control), intermediate (20 μg NH4+-N per gram of soil) and high (200 μg NH4+-N per gram of soil). Quantitative PCR demonstrated growth of AOA at all concentrations, whereas AOB growth was prominent only at the highest concentration. Similarly, denaturing gradient gel electrophoresis (DGGE) analysis revealed changes in AOA communities at all ammonium concentrations, whereas AOB communities changed significantly only at the highest ammonium concentration. These results provide evidence that ammonia concentration contributes to the definition of distinct ecological niches of AOA and AOB in soil. PMID:21228892

Measuring oxidative damage to DNA and its repair with the comet assay.

PubMed

Collins, Andrew R

2014-02-01

Single cell gel electrophoresis, or the comet assay, was devised as a sensitive method for detecting DNA strand breaks, at the level of individual cells. A simple modification, incorporating a digestion of DNA with a lesion-specific endonuclease, makes it possible to measure oxidised bases. With the inclusion of formamidopyrimidine DNA glycosylase to recognise oxidised purines, or Nth (endonuclease III) to detect oxidised pyrimidines, the comet assay has been used extensively in human biomonitoring to monitor oxidative stress, usually in peripheral blood mononuclear cells. There is evidence to suggest that the enzymic approach is more accurate than chromatographic methods, when applied to low background levels of base oxidation. However, there are potential problems of over-estimation (because the enzymes are not completely specific) or under-estimation (failure to detect lesions that are close together). Attempts have been made to improve the inter-laboratory reproducibility of the comet assay. In addition to measuring DNA damage, the assay can be used to monitor the cellular or in vitro repair of strand breaks or oxidised bases. It also has applications in assessing the antioxidant status of cells. In its various forms, the comet assay is now an invaluable tool in human biomonitoring and genotoxicity testing. This article is part of a Special Issue entitled Current methods to study reactive oxygen species - pros and cons and biophysics of membrane proteins. Guest Editor: Christine Winterbourn. Copyright © 2013 Elsevier B.V. All rights reserved.

The behaviour of entrainment defects formed in commercial purity Mg alloy cast under a cover gas of SF6

NASA Astrophysics Data System (ADS)

Li, T.; Griffiths, W. D.

2016-03-01

In the casting of light alloys, the oxidised film on the melt surface can be folded due to surface turbulence, thus forming entrainment defects that have a significant negative effect on the mechanical properties of castings. Previous researchers reported that the surface film of Mg alloys formed in an atmosphere containing SF6 had a complicated structure composed of MgO and MgF2. The work reported here aims to investigate the behaviour of entrainment defects formed in magnesium alloys protected by SF6-containing atmospheres. Tensile test bars of commercial purity Mg were cast in an unsealed environment under a cover gas of pure SF6. 34Scanning electron microscopy (SEM) of the fracture surface of the test bars indicated entrainment defects that consisted of symmetrical films containing MgO, but also sulphur and fluorine. The results of these examinations of the symmetrical films were used to infer the potential formation and development of entrainment defects in commercial purity Mg alloy.

Microstructures of ancient and modern cast silver–copper alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Northover, S.M., E-mail: s.m.northover@open.ac.uk; Northover, J.P., E-mail: peter.northover@materials.ox.ac.uk

The microstructures of modern cast Sterling silver and of cast silver objects about 2500 years old have been compared using optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), energy dispersive X-ray microanalysis (EDX) and electron backscatter diffraction (EBSD). Microstructures of both ancient and modern alloys were typified by silver-rich dendrites with a few pools of eutectic and occasional cuprite particles with an oxidised rim on the outer surface. EBSD showed the dendrites to have a complex internal structure, often involving extensive twinning. There was copious intragranular precipitation within the dendrites, in themore » form of very fine copper-rich rods which TEM, X-ray diffraction (XRD), SEM and STEM suggest to be of a metastable face-centred-cubic (FCC) phase with a cube–cube orientation relationship to the silver-rich matrix but a higher silver content than the copper-rich β in the eutectic. Samples from ancient objects displayed a wider range of microstructures including a fine scale interpenetration of the adjoining grains not seen in the modern material. Although this study found no unambiguous evidence that this resulted from microstructural change produced over archaeological time, the copper supersaturation remaining after intragranular precipitation suggests that such changes, previously proposed for wrought and annealed material, may indeed occur in ancient silver castings. - Highlights: • Similar twinned structures and oxidised surfaces seen in ancient and modern cast silver • General precipitation of fine Cu-rich rods apparently formed by discontinuous precipitation is characteristic of as-cast silver. • The fine rods are cube-cube related to the matrix in contrast with the eutectic. • The silver-rich phase remains supersaturated with copper. • Possibly age-related grain boundary features seen in ancient cast silver.« less

Chalcopyrite dissolution: Scanning photoelectron microscopy examination of the evolution of sulfur species with and without added iron or pyrite

NASA Astrophysics Data System (ADS)

Li, Yubiao; Qian, Gujie; Brown, Paul L.; Gerson, Andrea R.

2017-09-01

Dissolution and oxidation of sulfide minerals play key roles in both acid and metalliferous rock drainage and supergene enrichment. Surface speciation heterogeneity, critical to understanding mechanisms of mineral sulfide dissolution, has to date largely not been considered. To this end synchrotron scanning photoelectron microscopy (SPEM) was employed to examine freshly fractured and partially dissolved chalcopyrite (CuFeS2) surfaces (pH 1.0 HClO4 solution, redox potential 650 mV relative to a standard hydrogen electrode, 75 °C). S2- (bulk), S22- and Sn2- were found to be present on all samples at varying concentrations. Oxidation was observed to take place heterogeneously at the sub-micron scale. As compared to chalcopyrite partially dissolved for 5 days, extended dissolution to 10 days did not show appreciably enhanced oxidation of surface species; however surface roughness increased markedly due to the growth/overlap of oxidised sulfur species. On addition of 4 mM iron both S0 and SO42- were observed but not SO32-, indicating that the greater Fe3+ activity/concentration promotes heterogeneous sulfur oxidation. On contact of pyrite (FeS2) with chalcopyrite, significantly greater chalcopyrite surface oxidation was observed than for the other systems examined, with S0, SO32- and SO42- being identified heterogeneously across the surface. It is proposed that chalcopyrite oxidative dissolution is enhanced by increasing its cathodic area, e.g. contacting with pyrite, while increased Fe3+ activity/concentration also contributes to increased dissolution rates. The high degree of surface heterogeneity of these surface products indicates that these surfaces are not passivated by their formation. These results suggest that chalcopyrite dissolution will be accelerated when in contact with pyrite at solution redox potential intermediate between the rest potentials of chalcopyrite and pyrite (560 mV and 660 mV, respectively) and/or iron rich acidic waters with resulting enhanced formation of secondary sulfur containing species and release of copper and iron. This in turn suggests accelerated supergene formation and enhanced metalliferous drainage under these conditions.

Evidence of ancient microbial activity on Mars

NASA Astrophysics Data System (ADS)

Wallis, Jamie; Wickramasinghe, N. C.; Wallis, Daryl H.; Miyake, Nori; Wallis, M. K.; Hoover, Richard B.

2015-09-01

We report for the first time in situ observations of a relatively rare secondary iron arsenate-sulphate mineral named bukovskýite - Fe3+ 2(As5+O4)(S6+O4)(OH)•7(H2O) - found in a shock melt vein of the Tissint Martian meteorite. It is hypothesised that the mineral formed when high concentrations of aqueous H+, Fe(III), SO4 and AsO4 were maintained for long periods of time in microenvironments created within wet subsurface Martian clays. The aqueous H+, Fe(III), SO4 and AsO4 species arose from the microbial oxidation of FeS2 with concurrent release of sequestrated As. The availability of aqueous AsO4 would also be complemented by dissolution by-products of the microbial reduction of Feoxides influenced by dissolved organic matter that alters the redox state and the complexation of As, thus shifting As partitioning in favour of the solute phase. This hypothesis is substantially supported by SEM analysis of a 15μm spherical structure comprising of a carbonaceous outer coating with a inner core of FeS2 (pyrite) that showed the pyrite surface with spherical pits, and chains of pits, with morphologies distinct from abiotic alteration features. The pits and channels have a clustered, geometric distribution, typical of microbial activity, and are closely comparable to biologically mediated microstructures created by Fe- and S-oxidising microbes in the laboratory. These microstructures are interpreted as trace fossils resulting from the attachment of bacteria to the pyrite surfaces.

Criegee intermediates and their impacts on the troposphere

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khan, M. A. H.; Percival, C. J.; Caravan, R. L.

We report Criegee intermediates (CIs), carbonyl oxides formed in ozonolysis of alkenes, play key roles in the troposphere. The decomposition of CIs can be a significant source of OH to the tropospheric oxidation cycle especially during nighttime and winter months. A variety of model-measurement studies have estimated surface-level stabilized Criegee intermediate (sCI) concentrations on the order of 1 × 10 4 cm -3 to 1 × 10 5 cm -3, which makes a non-negligible contribution to the oxidising capacity in the terrestrial boundary layer. The reactions of sCI with the water monomer and the water dimer have been found tomore » be the most important bimolecular reactions to the tropospheric sCI loss rate, at least for the smallest carbonyl oxides; the products from these reactions (e.g. hydroxymethyl hydroperoxide, HMHP) are also of importance to the atmospheric oxidation cycle. The sCI can oxidise SO 2 to form SO 3, which can go on to form a significant amount of H 2SO 4 which is a key atmospheric nucleation species and therefore vital to the formation of clouds. Lastly, the sCI can also react with carboxylic acids, carbonyl compounds, alcohols, peroxy radicals and hydroperoxides, and the products of these reactions are likely to be highly oxygenated species, with low vapour pressures, that can lead to nucleation and SOA formation over terrestrial regions.« less

Oxygen content modulation by nanoscale chemical and electrical patterning in epitaxial SrCoO3-δ (0 < δ ≤ 0.5) thin films.

PubMed

Hu, S; Seidel, J

2016-08-12

Fast controllable redox reactions in solid materials at room temperature are a promising strategy for enhancing the overall performance and lifetime of many energy technology materials and devices. Easy control of oxygen content is a key concept for the realisation of fast catalysis and bulk diffusion at room temperature. Here, high quality epitaxial brownmillerite SrCoO2.5 thin films have been oxidised to perovskite (P) SrCoO3 with NaClO. X-ray diffraction, scanning probe microscopy and x-ray photoelectron spectroscopy measurements were performed to investigate the structural and electronic changes of the material. The oxidised thin films were found to exhibit distinct morphological changes from an atomically flat terrace structure to forming small nanosized islands with boundaries preferentially in [100] or [010] directions all over the surface, relaxing the in-plane strain imposed by the substrate. The conductivity, or oxygen content, of each single island is confined by these textures, which can be locally patterned even further with electric poling. The high charging level at the island boundaries indicates a magnified electric capacity of SCO thin films, which could be exploited in future device geometries. This finding represents a new way of oxygen modulation with associated self-assembled charge confinement to nanoscale boundaries, offering interesting prospects in nanotechnology applications.

Oxygen content modulation by nanoscale chemical and electrical patterning in epitaxial SrCoO3-δ (0 < δ ≤ 0.5) thin films

NASA Astrophysics Data System (ADS)

Hu, S.; Seidel, J.

2016-08-01

Fast controllable redox reactions in solid materials at room temperature are a promising strategy for enhancing the overall performance and lifetime of many energy technology materials and devices. Easy control of oxygen content is a key concept for the realisation of fast catalysis and bulk diffusion at room temperature. Here, high quality epitaxial brownmillerite SrCoO2.5 thin films have been oxidised to perovskite (P) SrCoO3 with NaClO. X-ray diffraction, scanning probe microscopy and x-ray photoelectron spectroscopy measurements were performed to investigate the structural and electronic changes of the material. The oxidised thin films were found to exhibit distinct morphological changes from an atomically flat terrace structure to forming small nanosized islands with boundaries preferentially in [100] or [010] directions all over the surface, relaxing the in-plane strain imposed by the substrate. The conductivity, or oxygen content, of each single island is confined by these textures, which can be locally patterned even further with electric poling. The high charging level at the island boundaries indicates a magnified electric capacity of SCO thin films, which could be exploited in future device geometries. This finding represents a new way of oxygen modulation with associated self-assembled charge confinement to nanoscale boundaries, offering interesting prospects in nanotechnology applications.

Criegee intermediates and their impacts on the troposphere

DOE PAGES

Khan, M. A. H.; Percival, C. J.; Caravan, R. L.; ...

2018-02-15

We report Criegee intermediates (CIs), carbonyl oxides formed in ozonolysis of alkenes, play key roles in the troposphere. The decomposition of CIs can be a significant source of OH to the tropospheric oxidation cycle especially during nighttime and winter months. A variety of model-measurement studies have estimated surface-level stabilized Criegee intermediate (sCI) concentrations on the order of 1 × 10 4 cm -3 to 1 × 10 5 cm -3, which makes a non-negligible contribution to the oxidising capacity in the terrestrial boundary layer. The reactions of sCI with the water monomer and the water dimer have been found tomore » be the most important bimolecular reactions to the tropospheric sCI loss rate, at least for the smallest carbonyl oxides; the products from these reactions (e.g. hydroxymethyl hydroperoxide, HMHP) are also of importance to the atmospheric oxidation cycle. The sCI can oxidise SO 2 to form SO 3, which can go on to form a significant amount of H 2SO 4 which is a key atmospheric nucleation species and therefore vital to the formation of clouds. Lastly, the sCI can also react with carboxylic acids, carbonyl compounds, alcohols, peroxy radicals and hydroperoxides, and the products of these reactions are likely to be highly oxygenated species, with low vapour pressures, that can lead to nucleation and SOA formation over terrestrial regions.« less

Cation profiling of passive films on stainless steel formed in sulphuric and acetic acid by deconvolution of angle-resolved X-ray photoelectron spectra

NASA Astrophysics Data System (ADS)

Högström, Jonas; Fredriksson, Wendy; Edstrom, Kristina; Björefors, Fredrik; Nyholm, Leif; Olsson, Claes-Olof A.

2013-11-01

An approach for determining depth gradients of metal-ion concentrations in passive films on stainless steel using angle-resolved X-ray photoelectron spectroscopy (ARXPS) is described. The iterative method, which is based on analyses of the oxidised metal peaks, provides increased precision and hence allows faster ARXPS measurements to be carried out. The method was used to determine the concentration depth profiles for molybdenum, iron and chromium in passive films on 316L/EN 1.4432 stainless steel samples oxidised in 0.5 M H2SO4 and acetic acid diluted with 0.02 M Na2B4O7 · 10H2O and 1 M H2O, respectively. The molybdenum concentration in the film is pin-pointed to the oxide/metal interface and the films also contained an iron-ion-enriched surface layer and a chromium-ion-dominated middle layer. Although films of similar composition and thickness (i.e., about 2 nm) were formed in the two electrolytes, the corrosion currents were found to be three orders of magnitude larger in the acetic acid solution. The differences in the layer composition, found for the two electrolytes as well as different oxidation conditions, can be explained based on the oxidation potentials of the metals and the dissolution rates of the different metal ions.

In-situ, time resolved monitoring of uranium in BFS:OPC grout. Part 1: Corrosion in water vapour.

PubMed

Stitt, C A; Paraskevoulakos, C; Banos, A; Harker, N J; Hallam, K R; Davenport, A; Street, S; Scott, T B

2017-08-11

Uranium encapsulated in grout was exposed to water vapour for extended periods of time. Through synchrotron x-ray powder diffraction and tomography measurements, uranium dioxide was determined the dominant corrosion product over a 50-week time period. The oxide growth rate initiated rapidly, with rates comparable to the U + H 2 O reaction. Over time, the reaction rate decreased and eventually plateaued to a rate similar to the U + H 2 O + O 2 reaction. This behaviour was not attributed to oxygen ingress, but instead the decreasing permeability of the grout, limiting oxidising species access to the metal surface.

Non-classical behaviour of higher valence dopants in chromium (III) oxide by a Cr vacancy compensation mechanism

NASA Astrophysics Data System (ADS)

Carey, John J.; Nolan, Michael

2017-10-01

Modification of metal oxides with dopants that have a stable oxidation in their parent oxides which is higher than the host system is expected to introduce extra electrons into the material to improve carrier mobility. This is essential for applications in catalysis, SOFCs and solar energy materials. Density functional theory calculations are used to investigate the change in electronic and geometric structure of chromium (III) oxide by higher valence dopants, namely; Ce, Ti, V and Zr. For single metal doping, we find that the dopants with variable oxidation states, Ce, Ti and V, adopt a valence state of  +3, while Zr dopant has a  +4 oxidation state and reduces a neighbouring Cr cation. Chromium vacancy formation is greatly enhanced for all dopants, and favoured over oxygen vacancy formation. The Cr vacancies generate holes which oxidise Ce, Ti and V from  +3 to  +4, while also oxidising lattice oxygen sites. For Zr doping, the generated holes oxidise the reduced Cr2+ cation back to Cr3+ and also two lattice oxygen atoms. Three metal atoms in the bulk lattice facilitate spontaneous Cr vacancy from charge compensation. A non-classical compensation mechanism is observed for Ce, Ti and V; all three metals are oxidised from  +3 to  +4, which explains experimental observations that these metals have a  +4 oxidation state in Cr2O3. Charge compensation of the three Zr metals proceeds by a classical higher valence doping mechanism; the three dopants reduce three Cr cations, which are subsequently charge compensated by a Cr vacancy oxidising three Cr2+ to Cr3+. The compensated structures are the correct ground state electronic structure for these doped systems, and used as a platform to investigate cation/anion vacancy formation. Unlike the single metal doped bulks, preference is now given for oxygen vacancy formation over Cr vacancy formation, indicating that the dopants increase the reducibility of Cr2O3 with Ce doping showing the strongest enhancement. The importance of the correct ground state in determining the formation of defects is emphasised.

Implementation of steady state approximation for modelling of reaction kinetic of UV catalysed hydrogen peroxide oxidation of starch

NASA Astrophysics Data System (ADS)

Kumoro, Andri Cahyo; Retnowati, Diah Susetyo; Ratnawati, Budiyati, Catarina Sri

2015-12-01

With regard to its low viscosity, high stability, clarity, film forming and binding properties, oxidised starch has been widely used in various applications specifically in the food, paper, textile, laundry finishing and binding materials industries. A number of methods have been used to produce oxidised starch through reactions with various oxidizing agents, such as hydrogen peroxide, air oxygen, ozone, bromine, chromic acid, permanganate, nitrogen dioxide and hypochlorite. Unfortunately, most of previous works reported in the literatures were focused on the study of reaction mechanism and physicochemical properties characterization of the oxidised starches produced without investigation of the reaction kinetics of the oxidation process. This work aimed to develop a simple kinetic model for UV catalysed hydrogen peroxide oxidation of starch through implementation of steady state approximation for the radical reaction rates. The model was then verified using experimental data available in the literature. The model verification revealed that the proposed model shows its good agreement with the experimental data as indicated by an average absolute relative error of only 2.45%. The model also confirmed that carboxyl groups are oxidised further by hydroxyl radical. The carbonyl production rate was found to follow first order reaction with respect to carbonyl concentration. Similarly, carboxyl production rate also followed first order reaction with respect to carbonyl concentration. The apparent reaction rate constant for carbonyl formation and oxidation were 6.24 × 104 s-1 and 1.01 × 104 M-1.s-1, respectively. While apparent reaction rate constant for carboxyl oxidation was 4.86 × 104 M-1.s-1.

Short-term static corrosion tests in lead-bismuth

NASA Astrophysics Data System (ADS)

Soler Crespo, L.; Martín Muñoz, F. J.; Gómez Briceño, D.

2001-07-01

Martensitic steels have been proposed to be used as structural materials and as spallation target window in hybrid systems devoted to the transmutation of radioactive waste of long life and high activity. However, their compatibility with lead-bismuth in the operating conditions of these systems depends on the existence of a protective layer such as an oxide film. The feasibility of forming and maintaining an oxide layer or maintaining a pre-oxidised one has been studied. Martensitic steel F82Hmod. (8% Cr) has been tested in lead-bismuth under static and isothermal conditions at 400°C and 600°C. In order to study the first stages of the interaction between the steel and the eutectic, short-term tests (100 and 665 h) have been carried out. Pre-oxidised and as-received samples have been tested in atmospheres with different oxidant potential. For low oxygen concentration in lead-bismuth due to unexpected oxygen consumption in the experimental device, dissolution of as-received F82Hmod. occurs and pre-oxidation does not prevent the material dissolution. For high oxygen concentration, the pre-oxidation layer seems to improve the feasibility of protecting stainless steels controlling the oxygen potential of lead-bismuth with a gas phase.

Sucrose tricarboxylate by sonocatalysed TEMPO-mediated oxidation.

PubMed

Lemoine, S; Thomazeau, C; Joannard, D; Trombotto, S; Descotes, G; Bouchu, A; Queneau, Y

2000-06-16

Oxidation of sucrose by the NaOCl/TEMPO system provided sucrose tricarboxylate without the addition of sodium bromide as co-catalyst when high-frequency (500 kHz) ultrasound was applied, in contrast to very limited conversion without sonication. In the presence of sodium bromide, sonication also caused acceleration of the oxidation. The rate increase due to sonication of the oxidant system prior to sucrose addition suggests that ultrasound acts at the level of the formation of the nitrosonium ion, the active oxidising species in the catalytic cycle.

Prospective and randomised evaluation of the protease-modulating effect of oxidised regenerated cellulose/collagen matrix treatment in pressure sore ulcers.

PubMed

Kloeters, Oliver; Unglaub, Frank; de Laat, Erik; van Abeelen, Marjolijn; Ulrich, Dietmar

2016-12-01

In chronic wounds, excess levels and activity of proteases such as elastase and plasmin have been detected. Oxidised regenerated cellulose/collagen matrix (ORC/collagen matrix) has been reported to ameliorate the wound microenvironment by binding and inactivating excess proteases in wound exudates. In this study, the levels and activity of elastase and plasmin in wound exudates of pressure sore ulcers were measured to determine the beneficial effect of ORC/collagen matrix treatment compared with control treatment with a foam dressing. A total of 33 patients with pressure sores were enrolled in the study and were followed up for 12 weeks after treatment. Ten control patients were treated with a foam hydropolymer dressing (TIELLE ® , Systagenix), and the remaining 23 patients were treated with ORC/collagen matrix plus the foam dressing (TIELLE ® , Systagenix) on top. Wound assessments were carried out over 12 weeks on a weekly basis, with dressing changes twice a week. Ulcers were photographed and wound exudates were collected on admission and at days 5, 14 and then every 14 days to provide a visual record of any changes in appearance of the ulcer and healing rate and for biochemical analysis of the wound. The levels and activity of elastase and plasmin were measured in wound exudates. Statistical analysis was performed using ANOVA and Bonferroni's post hoc test with P-values <0·05 considered to be significant. Compared with controls, ORC/collagen matrix-treated pressure sore wounds showed a significant faster healing rate, which positively correlated with a decreased activity of elastase and plasmin in wound exudates. No signs of infection or intolerance to the ORC/collagen matrix were observed. © 2015 Medicalhelplines.com Inc and John Wiley & Sons Ltd.

Chromosome and oxidative damage biomarkers in lymphocytes of Parkinson's disease patients.

PubMed

Migliore, L; Scarpato, R; Coppede, F; Petrozzi, L; Bonuccelli, U; Rodilla, V

2001-10-01

As cancer development usually results from exposure to several environmental risk factors in interaction with the genetic susceptibility of the host, it could be of interest to investigate if neurodegeneration, as occurs in Parkinson's disease (PD) patients can be attributed at least partially, to environmental risk factors. There is growing evidence that oxidative stress could play a significant role as a risk factor in the aetiology and pathogenesis of neurodegenerative diseases, emphasising the need for new individual and human-based approaches. The aim of our research is to explore the relation between chromosome instability and oxidative stress biomarkers in Parkinson's disease using a variety of strategies. We determined peripheral markers for oxidative damage in PD by testing for spontaneous and induced chromosomal damage, DNA strand breaks, oxidised pyrimidines and altered purines both in peripheral blood and cultured lymphocytes. We also measured glutathione S-transferase activity in the plasma of patients and controls. Compared to healthy controls, PD patients show higher frequencies of micronuclei (17.2 +/- 4.8 vs. 9.0 +/- 3.4, p < 0.001) and a significant increase in the levels of single strand breaks (SSB). Significant differences were also obtained in the distribution of oxidised purine bases between the two groups. Preliminary data obtained by fluorescence in situ hybridization analysis showed that the percentage of centromere negative micronuclei is higher than that of centromere positive micronuclei. Glutathione S-transferase activity in plasma from PD patients and controls was also measured and the enzymatic activity in PD patients was lower than in healthy controls.

Counterflow diffusion flames: effects of thermal expansion and non-unity Lewis numbers

NASA Astrophysics Data System (ADS)

Koundinyan, Sushilkumar P.; Matalon, Moshe; Stewart, D. Scott

2018-05-01

In this work we re-examine the counterflow diffusion flame problem focusing in particular on the flame-flow interactions due to thermal expansion and its influence on various flame properties such as flame location, flame temperature, reactant leakage and extinction conditions. The analysis follows two different procedures: an asymptotic approximation for large activation energy chemical reactions, and a direct numerical approach. The asymptotic treatment follows the general theory of Cheatham and Matalon, which consists of a free-boundary problem with jump conditions across the surface representing the reaction sheet, and is well suited for variable-density flows and for mixtures with non-unity and distinct Lewis numbers for the fuel and oxidiser. Due to density variations, the species and energy transport equations are coupled to the Navier-Stokes equations and the problem does not possess an analytical solution. We thus propose and implement a methodology for solving the free-boundary problem numerically. Results based on the asymptotic approximation are then verified against those obtained from the 'exact' numerical integration of the governing equations, comparing predictions of the various flame properties.

Anammox process for nitrogen removal from anaerobically digested fish canning effluents.

PubMed

Dapena-Mora, A; Campos, J L; Mosquera-Corral, A; Méndez, R

2006-01-01

The Anammox process was used to treat the effluent generated in an anaerobic digester which treated the wastewater from a fish cannery once previously processed in a Sharon reactor. The effluents generated from the anaerobic digestion are characterised by their high ammonium content (700-1000 g NH4+ -Nm(-3)), organic carbon content (1000-1300 g TOCm(-3)) and salinity up to 8,000-10,000 g NaCl m(-3). In the Sharon reactor, approximately 50% of the NH4+ -N was oxidised to NO2- -N via partial nitrification. The effluent of the Sharon step was fed to the Anammox reactor which treated an averaged nitrogen loading rate of 500 g N m(-3) x d(-1). The system reached an averaged nitrogen removal efficiency of 68%, mainly limited due to the nonstoichiometric relation, for the Anammox process, between the ammonium and nitrite added in the feeding. The Anammox reactor bacterial population distribution, followed by FISH analysis and batch activity assays, did not change significantly despite the continuous entrance to the system of aerobic ammonium oxidisers coming from the Sharon reactor. Most of the bacteria corresponded to the Anammox population and the rest with slight variable shares to the ammonia oxidisers. The Anammox reactor showed an unexpected robustness despite the continuous variations in the influent composition regarding ammonium and nitrite concentrations. Only in the period when NO2- -N concentration was higher than the NH4+ -N concentration did the process destabilise and it took 14 days until the nitrogen removal percentage decreased to 34% with concentrations in the effluent of 340g NH4+ -N m(-3) and 440 g NO2- -N m(-3), respectively. Based on these results, it seems that the Sharon-Anammox system can be applied for the treatment of industrial wastewaters with high nitrogen load and salt concentration with an appropriate control of the NO2- -N/NH4+ -N ratio.

Toxic effects of butyl elastomers on aerobic methane oxidation

NASA Astrophysics Data System (ADS)

Niemann, Helge; Steinle, Lea I.; Blees, Jan H.; Krause, Stefan; Bussmann, Ingeborg; Lehmann, Moritz F.; Treude, Tina

2013-04-01

Large quantities of the potent greenhouse gas methane are liberated into the water column of marine and lacustrine environments where it may be consumed by aerobic methane oxidising bacteria before reaching the atmosphere.The reliable quantification of aerobic methane oxidation (MOx) rates is consequently of paramount importance for estimating methane budgets and to understand the controls on water column methane cycling. A widely used set of methods for measuring MOx rates is based on the incubation of water samples during which the consumption of methane is monitored, for instance with radio-tracer assays. Typically, incubation vessels are sealed with butyl rubber stoppers because these elastomers are essentially impermeable for gases at the relevant time scales. We tested the effect of different stopper materials (unmodified- and halogenated butyl rubber) on MOx activity in environmental samples and in cultures of methane oxidising bacteria. MOx rates in samples sealed with unmodified butyl rubber were > 75% lower compared to parallel incubations with halogenated butyl rubber seals, suggesting inhibiting/toxic effects associated with the use of unmodified butyl elastomers. To further explore the cause of these effects, we analysed aqueous extracts of the different stoppers. Halogenated butyl rubber stoppers appeared to bleed off comparably little amounts of organics. In stark contrast, extracts of unmodified butyl rubber were contaminated with various organic compounds including potential bactericides such as benzyltoluenes, phenylalkanes and benzuothiazoles. We also found tetramethylthiourea, a scavenger of active oxygen species, which may inhibit the MOx pathway.

Water adsorption on the P-rich GaP(100) surface: optical spectroscopy from first principles

NASA Astrophysics Data System (ADS)

May, Matthias M.; Sprik, Michiel

2018-03-01

The contact of water with semiconductors typically changes its surface electronic structure by oxidation or corrosion processes. A detailed knowledge—or even control of—the surface structure is highly desirable, as it impacts the performance of opto-electronic devices from gas-sensing to energy conversion applications. It is also a prerequisite for density functional theory-based modelling of the electronic structure in contact with an electrolyte. The P-rich GaP(100) surface is extraordinary with respect to its contact with gas-phase water, as it undergoes a surface reordering, but does not oxidise. We investigate the underlying changes of the surface in contact with water by means of theoretically derived reflection anisotropy spectroscopy (RAS). A comparison of our results with experiment reveals that a water-induced hydrogen-rich phase on the surface is compatible with the boundary conditions from experiment, reproducing the optical spectra. We discuss potential reaction paths that comprise a water-enhanced hydrogen mobility on the surface. Our results also show that computational RAS—required for the interpretation of experimental signatures—is feasible for GaP in contact with water double layers. Here, RAS is sensitive to surface electric fields, which are an important ingredient of the Helmholtz-layer. This paves the way for future investigations of RAS at the semiconductor–electrolyte interface.

The Mars Simulation Laboratory, University of Aarhus

NASA Astrophysics Data System (ADS)

Merrison, J. P.; Field, D.; Finster, K.; Lomstein, B. Aa.; Nørnberg, P.; Ramsing, N. B.; Uggerhøj, E.

2001-08-01

Present day Mars presents an extremely hostile environment to organic material. The average temperature is low (-50C), the atmospheric pressure is also low (7mbar) and there is little water over most of the planet. Chemically the surface is extremely oxidising and no signs of organic material have been detected. There is also a strong component of ultra violet radiation in the Martian sun light, lethal to most organisms. At Aarhus University we have constructed a Mars simulation environment which reproduces the physical, chemical and mineralogical conditions on Mars. It is hoped to set limits on where organic matter (or even life) might exist on Mars, for example at some depth under the surface, beneath the polar ice or within rocks. It is also possible to adjust the conditions in the simulation to investigate the most extreme environments in which organisms can be preserved or still function.

Hydroxytyrosol in functional hydroxytyrosol-enriched biscuits is highly bioavailable and decreases oxidised low density lipoprotein levels in humans.

PubMed

Mateos, Raquel; Martínez-López, Sara; Baeza Arévalo, Gema; Amigo-Benavent, Miryam; Sarriá, Beatriz; Bravo-Clemente, Laura

2016-08-15

Hydroxytyrosol (HT) and its derivatives in olive oil protect low-density lipoproteins (LDL) against oxidation. Biscuits could be a convenient alternative to broaden consumers' choice of HT-rich foods, although the biscuit matrix could affect HT bioavailability. We performed a crossover, randomized, double-blind study to evaluate HT bioavailability in HT-enriched biscuits (HT-B) versus non-enriched biscuits (C-B), and the effects on oxidative postprandial status. On two separate days, 13 subjects consumed 30 g of C-B or HT-B (5.25mg HT) after overnight-fasting. Blood and urine were collected at different intervals and analysed by LC-MS-QToF. After HT-B consumption, plasma metabolites peaked between 0.5 and 1h and were extensively excreted in urine. HT-sulphate and 3,4-dihydroxyphenylacetic acid (DOPAC)-sulphate were the main metabolites, followed by DOPAC and homovanillic acid (HVA). HT-glucuronide, DOPAC-glucuronide, HVA-glucuronide and HVA-sulphate were also detected. Postprandial oxidised-LDL concentrations decreased with HT-B. HT is a promising functional ingredient and, in biscuits, it is highly bioavailable and lowers postprandial oxidised-LDL levels. Copyright © 2016 Elsevier Ltd. All rights reserved.

Robotic astrobiology - the need for sub-surface penetration of Mars

NASA Astrophysics Data System (ADS)

Ellery, A.; Ball, A.; Cockell, C.; Coste, P.; Dickensheets, D.; Edwards, H.; Hu, H.; Kolb, C.; Lammer, H.; Lorenz, R.; McKee, G.; Richter, L.; Winfield, A.; Welch, C.

2002-11-01

Recent interest in the astrobiological investigation of Mars has culminated in the only planned astrobiology-focussed robotic mission to Mars - the Beagle2 mission to be carried to Mars by the Mars Express spacecraft in 2003. Beagle2 will be primarily investigating the surface and near-surface environment of Mars. However, the results from the Viking Mars lander indicated that the Martian surface is saturated in peroxides and super-oxides which would rapidly degrade any organic material. Furthermore, recent models of gardening due to meteoritic impacts on the Martian surface suggest that the depth of this oxidising layer could extend to depths of 2-3m. Given that the discovery of organic fossilised residues will be the primary target for astrobiological investigation, this implies that future robotic astrobiology missions to Mars must penetrate to below these depths. The need to penetrate into the sub-surface of Mars has recently been given greater urgency with the discovery of extensive water ice-fields as little as 1m from the surface. We review the different technologies that make this penetration into the sub-surface a practical possibility on robotic missions. We further briefly present one such implementation of these technologies through the use of ground-penetrating moles - The Vanguard Mars mission proposal.

Oxidation of UC: An in situ high temperature environmental scanning electron microscopy study

NASA Astrophysics Data System (ADS)

Gasparrini, Claudia; Podor, Renaud; Horlait, Denis; Rushton, Michael J. D.; Fiquet, Olivier; Lee, William Edward

2017-10-01

In situ HT-ESEM oxidation of sintered UC fragments revealed the morphological changes occurring during the transformation between UC to UO2 and UO2 to U3O8 at 723-848 K and in an atmosphere of 10-100 Pa O2. Two main oxidation pathways were revealed. Oxidation at 723 K in atmospheres ≤25 Pa O2 showed the transformation from UC to UO2+x, as confirmed by post mortem HRTEM analysis. This oxidation pathway was comprised of three steps: (i) an induction period, where only surface UC particles oxidised, (ii) a sample area expansion accompanied by crack formation and propagation, (iii) a stabilisation of the total crack length inferring that crack propagation had stopped. Samples oxidised under 50 Pa O2 at 723 K and at 773-848 K for 10-100 Pa O2 showed an "explosive" oxidation pathway: (i) sample area expansion occurred as soon as oxygen was inserted into the chamber and crack propagation and crack length followed an exponential law; (ii) cracks propagated as a network and the oxide layer fragmented, (iii) an "explosion" occurred causing a popcorn-like transformation, typical for oxidation from UO2 to U3O8. HRTEM characterisation revealed U3O8 preferentially grow in the [001] direction. The explosive growth, triggered by ignition of UC, proceeded as a self-propagating high-temperature synthesis reaction, with a propagation speed of 150-500 ± 50 μm/s.

The mechanism of formation, structure and physiological relevance of covalent hemoglobin attachment to the erythrocyte membrane.

PubMed

Welbourn, Elizabeth M; Wilson, Michael T; Yusof, Ashril; Metodiev, Metodi V; Cooper, Chris E

2017-02-01

Covalent hemoglobin binding to membranes leads to band 3 (AE1) clustering and the removal of erythrocytes from the circulation; it is also implicated in blood storage lesions. Damaged hemoglobin, with the heme being in a redox and oxygen-binding inactive hemichrome form, has been implicated as the binding species. However, previous studies used strong non-physiological oxidants. In vivo hemoglobin is constantly being oxidised to methemoglobin (ferric), with around 1% of hemoglobin being in this form at any one time. In this study we tested the ability of the natural oxidised form of hemoglobin (methemoglobin) in the presence or absence of the physiological oxidant hydrogen peroxide to initiate membrane binding. The higher the oxidation state of hemoglobin (from Fe(III) to Fe(V)) the more binding was observed, with approximately 50% of this binding requiring reactive sulphydryl groups. The hemoglobin bound was in a high molecular weight complex containing spectrin, ankyrin and band 4.2, which are common to one of the cytoskeletal nodes. Unusually, we showed that hemoglobin bound in this way was redox active and capable of ligand binding. It can initiate lipid peroxidation showing the potential to cause cell damage. In vivo oxidative stress studies using extreme endurance exercise challenges showed an increase in hemoglobin membrane binding, especially in older cells with lower levels of antioxidant enzymes. These are then targeted for destruction. We propose a model where mild oxidative stress initiates the binding of redox active hemoglobin to the membrane. The maximum lifetime of the erythrocyte is thus governed by the redox activity of the cell; from the moment of its release into the circulation the timer is set. Copyright © 2016. Published by Elsevier Inc.

Turning Cellulose Waste Into Electricity: Hydrogen Conversion by a Hydrogenase Electrode

PubMed Central

Abramov, Sergey M.; Sadraddinova, Elmira R.; Shestakov, Andrey I.; Voronin, Oleg G.; Karyakin, Arkadiy A.; Zorin, Nikolay A.; Netrusov, Alexander I.

2013-01-01

Hydrogen-producing thermophilic cellulolytic microorganisms were isolated from cow faeces. Rates of cellulose hydrolysis and hydrogen formation were 0.2 mM L-1 h-1 and 1 mM L-1 h-1, respectively. An enzymatic fuel cell (EFC) with a hydrogenase anode was used to oxidise hydrogen produced in a microbial bioreactor. The hydrogenase electrode was exposed for 38 days (912 h) to a thermophilic fermentation medium. The hydrogenase activity remaining after continuous operation under load was 73% of the initial value. PMID:24312437

From source to sink: Rare-earth elements trace the legacy of sulfuric dredge spoils on estuarine sediments.

PubMed

Xu, Nian; Morgan, Bree; Rate, Andrew W

2018-05-17

Land disposal of dredged sulfide-rich coastal sediments generates secondary coastal acid sulfate soils (CASS), as previously reduced sulfide minerals oxidise to produce acidic drainage rich in Fe, SO 4 2- and rare-earth elements (REEs). Few studies investigate both the source and the sink of REEs in the context of interpreting their mobilisation and potential use in tracing anthropogenic activity. Here we investigate REE signatures in estuarine sediments (and overlying surface waters) that have received acute, long-term (>15 years) acidic drainage from legacy sulfuric dredge spoils. It was found that the dredge spoil continues to act as a source of acidity (pH 3.5-5.5), Fe and REEs during development of CASS, and contains negligible acid volatile sulfide (AVS, a proxy for FeS) and relatively low concentrations of ΣREE (mean 44.5 mg/kg, range 4.1-362 mg/kg). In the receiving sediments, high AVS concentrations (mean 92.2 μmol/g, range 0.38-278 μmol/g) reflect elevated FeS content, likely due to high inputs of Fe and SO 4 2- from the acidic drainage, and correspond with a high concentration of total S (mean 852 μmol/g, range 105-2209 μmol/g) and an accumulation of ΣREE (mean 670 mg/kg, range 19.9-1819 mg/kg). Importantly, where drain sediments that were previously enriched in highly reactive sulfidic minerals and trace elements and have become exposed to the atmosphere (e.g. Site 3) and partially oxidised, they provide a further source of acidification, remobilising the REEs to the downstream sediments. Interestingly, we also found a clear positive correlation between phosphorous and REEs both in the dredge spoil and sediment, suggesting phosphate minerals may act as a sink for REEs in CASS influenced drain sediments. This is further supported by strong positive gadolinium anomalies (1.1-1.6) and high calculated anthropogenic Gd values (12-38%), which may reflect the influence of phosphate fertiliser on this eutrophic system. Copyright © 2018 Elsevier B.V. All rights reserved.

Reactions of inorganic free radicals with liver protecting drugs

NASA Astrophysics Data System (ADS)

György, I.; Blázovics, A.; Fehér, J.; Földiák, G.

Liver protecting drugs, silibinin, a flavonolignane, and the dihydroquinoline derivates, CH 402 and MTDQ-DA, were shown to inhibit processes in which enzymatically or non-enzymatically generated free radicals were involved. Inorganic free radicals (N 3, (SCN) -2, OH, Trp, CO -2, O -2) produced by pulse radiolysis readily react with the compounds, which transform into exceptionally long-lived, unreactive transients. Time evolution of the UV and visible spectra indicate that oxidising radicals form a phenoxyl type radical from silibinin, while OH forms an adduct by attacking, simultaneously, at various sites of the molecule. Superoxide radicals reduce silibinin and oxidise CH 402 and MTDQ-DA. It is concluded that the drugs might exhibit antioxidant behavior in living systems.

Removing organic and nitrogen content from a highly saline municipal wastewater reverse osmosis concentrate by UV/H2O2-BAC treatment.

PubMed

Pradhan, Shovana; Fan, Linhua; Roddick, Felicity A

2015-10-01

Reverse osmosis (RO) concentrate (ROC) streams generated from RO-based municipal wastewater reclamation processes pose potential health and environmental risks on their disposal to confined water bodies such as bays. A UV/H2O2 advanced oxidation process followed by a biological activated carbon (BAC) treatment was evaluated at lab-scale for the removal of organic and nutrient content from a highly saline ROC (TDS 16 g L(-1), EC 23.5 mS cm(-1)) for its safe disposal to the receiving environment. Over the 230-day operation of the UV/H2O2-BAC process, the colour and UV absorbance (254 nm) of the ROC were reduced to well below those of the influent to the reclamation process. The concentrations of DOC and total nitrogen (TN) were reduced by approximately 60% at an empty bed contact time (EBCT) of 60 min. The reduction in ammonia nitrogen by the BAC remained high under all conditions tested (>90%). Further investigation confirmed that the presence of residual peroxide in the UV/H2O2 treated ROC was beneficial for DOC removal, but markedly inhibited the activities of the nitrifying bacteria (i.e., nitrite oxidising bacteria) in the BAC system and hence compromised total nitrogen removal. This work demonstrated that the BAC treatment could be acclimated to the very high salinity environment, and could be used as a robust method for the removal of organic matter and nitrogen from the pre-oxidised ROC under optimised conditions. Copyright © 2015 Elsevier Ltd. All rights reserved.

Amino acid homeostasis and signalling in mammalian cells and organisms

PubMed Central

Bröer, Angelika

2017-01-01

Cells have a constant turnover of proteins that recycle most amino acids over time. Net loss is mainly due to amino acid oxidation. Homeostasis is achieved through exchange of essential amino acids with non-essential amino acids and the transfer of amino groups from oxidised amino acids to amino acid biosynthesis. This homeostatic condition is maintained through an active mTORC1 complex. Under amino acid depletion, mTORC1 is inactivated. This increases the breakdown of cellular proteins through autophagy and reduces protein biosynthesis. The general control non-derepressable 2/ATF4 pathway may be activated in addition, resulting in transcription of genes involved in amino acid transport and biosynthesis of non-essential amino acids. Metabolism is autoregulated to minimise oxidation of amino acids. Systemic amino acid levels are also tightly regulated. Food intake briefly increases plasma amino acid levels, which stimulates insulin release and mTOR-dependent protein synthesis in muscle. Excess amino acids are oxidised, resulting in increased urea production. Short-term fasting does not result in depletion of plasma amino acids due to reduced protein synthesis and the onset of autophagy. Owing to the fact that half of all amino acids are essential, reduction in protein synthesis and amino acid oxidation are the only two measures to reduce amino acid demand. Long-term malnutrition causes depletion of plasma amino acids. The CNS appears to generate a protein-specific response upon amino acid depletion, resulting in avoidance of an inadequate diet. High protein levels, in contrast, contribute together with other nutrients to a reduction in food intake. PMID:28546457

Barley yellow dwarf virus infection and elevated CO2 alter the antioxidants ascorbate and glutathione in wheat.

PubMed

Vandegeer, Rebecca K; Powell, Kevin S; Tausz, Michael

2016-07-20

Plant antioxidants ascorbate and glutathione play an important role in regulating potentially harmful reactive oxygen species produced in response to virus infection. Barley yellow dwarf virus is a widespread viral pathogen that systemically infects cereal crops including wheat, barley and oats. In addition, rising atmospheric CO 2 will alter plant growth and metabolism, including many potential but not well understood effects on plant-virus interactions. In order to better understand the wheat-BYDV interaction and any potential changes under elevated CO 2 , the total concentration and oxidised fraction of ascorbate and glutathione was measured in leaves of a susceptible wheat cultivar (Triticum aestivum L. 'Yitpi') infected with Barley yellow dwarf virus-PAV (Padi Avenae virus) and grown under elevated CO 2 in controlled environment chambers. Virus infection decreased total leaf ascorbate and glutathione concentrations and increased the fraction of oxidised ascorbate (dehydroascorbate). Elevated CO 2 decreased the fraction of oxidised ascorbate. In this work, we demonstrate that systemic infection by a phloem-restricted virus weakens the antioxidant pools of ascorbate and glutathione. In addition, elevated CO 2 may decrease oxidative stress, for example, from virus infection, but there was no direct evidence for an interactive effect between treatments. Copyright © 2016 Elsevier GmbH. All rights reserved.

Disposition and metabolism of [14C]lemborexant, a novel dual orexin receptor antagonist, in rats and monkeys.

PubMed

Ueno, Takashi; Ishida, Tomomi; Kusano, Kazutomi

2018-05-28

1. The disposition and metabolism of lemborexant, a novel dual orexin receptor antagonist currently under development as a therapeutic agent for insomnia disorder, were evaluated after a single oral administration of [ 14 C]lemborexant in Sprague-Dawley rats (10 mg/kg) and cynomolgus monkeys (3 mg/kg). 2. In both species, [ 14 C]lemborexant was rapidly absorbed: radioactivity concentration in blood peaked at 0.83-1.8 h, and decreased with elimination half-life of 110 h. The radioactivity administered was excreted primarily into faeces, with relatively little excreted into urine. 3. Lemborexant was not detected in bile, urine, or faeces, indicating that lemborexant administered orally was completely absorbed from the gastrointestinal tract and that the main elimination pathway was metabolism in both species. 4. In rats, lemborexant was found to be minor in plasma (≤5.2% of total radioactivity), and M9 (hydroxylated form) was the major circulating metabolite. In monkeys, the major circulating components were lemborexant, M4 (N-oxide metabolite), M13 (di-oxidised form), M14 (di-oxidised form), and M16 (glucuronide of mono-oxidised form). 5. In both species, lemborexant was metabolised to various metabolites by multiple pathways, the primary of which was oxidation of the dimethylpyrimidine or fluorophenyl moiety.

Effects of high energy electrons on the properties of polyethylene / multiwalled carbon nanotubes composites: Comparison of as-grown and oxygen-functionalised MWCNT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krause, B., E-mail: krause-beate@ipfdd.de, E-mail: poe@ipfdd.de, E-mail: gohs@ipfdd.de; Pötschke, P., E-mail: krause-beate@ipfdd.de, E-mail: poe@ipfdd.de, E-mail: gohs@ipfdd.de; Gohs, U., E-mail: krause-beate@ipfdd.de, E-mail: poe@ipfdd.de, E-mail: gohs@ipfdd.de

2014-05-15

Polymer modification with high energy electrons (EB) is well established in different applications for many years. It is used for crosslinking, curing, degrading, grafting of polymeric materials and polymerisation of monomers. In contrast to this traditional method, electron induced reactive processing (EIReP) combines the polymer modification with high energy electrons and the melt mixing process. This novel reactive method was used to prepare polymer blends and composites. In this study, both methods were used for the preparation of polyethylene (PE)/ multiwalled carbon nanotubes (MWCNT) composites in the presence of a coupling agent. The influence of MWCNT and type of electronmore » treatment on the gel content, the thermal conductivity, rheological, and electrical properties was investigated whereby as-grown and oxidised MWCNT were used. In the presence of a coupling agent and at an absorbed dose of 40 kGy, the gel content increased from 57 % for the pure PE to 74 % or 88 % by the addition of as-grown (Baytubes® C150P) or oxidised MWCNT, respectively. In comparison to the composites containing the as-grown MWCNTs, the use of the oxidised MWCNTs led to higher melt viscosity and higher storage modulus due to higher yield of filler polymer couplings. The melt viscosity increased due to the addition of MWCNT and crosslinking of PE. The thermal conductivity increased to about 150 % and showed no dependence on the kind of MWCNT and the type of electron treatment. In contrast, the lowest value of electrical volume resistivity was found for the non-irradiated samples and after state of the art electron treatment without any influence of the type of MWCNT. In the case of EIReP, the volume resistivity increased by 2 (as-grown MWCNT) or 3 decades (oxidised MWCNT) depending on the process parameters.« less

A study on the relationships between corrosion properties and chemistry of thermally oxidised surface films formed on polished commercial magnesium alloys AZ31 and AZ61

NASA Astrophysics Data System (ADS)

Feliu, Sebastián; Samaniego, Alejandro; Barranco, Violeta; El-Hadad, A. A.; Llorente, Irene; Serra, Carmen; Galván, J. C.

2014-03-01

This paper studies the changes in chemical composition of the thin oxide surface films induced by heating in air at 200 °C for time intervals from 5 min to 60 min on the freshly polished commercial AZ31 and AZ61 alloys with a view to better understanding their protective properties. This thermal treatment resulted in the formation of layers enriched in metallic aluminium at the interface between the outer MgO surface films and the bulk material. A strong link was found between the degree of metallic Al enrichment in the subsurface layer (from 10 to 15 at.%) observed by XPS (X-ray photoelectron spectroscopy) in the AZ61 treated samples and the increase in protective properties observed by EIS (electrochemical impedance spectroscopy) in the immersion test in 0.6 M NaCl. Heating for 5-60 min in air at 200 °C seems to be an effective, easy to perform and inexpensive method for increasing the corrosion resistance of the AZ61 alloy by approximately two or three times.

Dynamic viscosity mapping of the oxidation of squalene aerosol particles.

PubMed

Athanasiadis, Athanasios; Fitzgerald, Clare; Davidson, Nicholas M; Giorio, Chiara; Botchway, Stanley W; Ward, Andrew D; Kalberer, Markus; Pope, Francis D; Kuimova, Marina K

2016-11-09

Organic aerosols (OAs) play important roles in multiple atmospheric processes, including climate change, and can impact human health. The physico-chemical properties of OAs are important for all these processes and can evolve through reactions with various atmospheric components, including oxidants. The dynamic nature of these reactions makes it challenging to obtain a true representation of their composition and surface chemistry. Here we investigate the microscopic viscosity of the model OA composed of squalene, undergoing chemical aging. We employ Fluorescent Lifetime Imaging Microscopy (FLIM) in conjunction with viscosity sensitive probes termed molecular rotors, in order to image the changes in microviscosity in real time during oxidation with ozone and hydroxyl radicals, which are two key oxidising species in the troposphere. We also recorded the Raman spectra of the levitated particles to follow the reactivity during particle ozonolysis. The levitation of droplets was achieved via optical trapping that enabled simultaneous levitation and measurement via FLIM or Raman spectroscopy and allowed the true aerosol phase to be probed. Our data revealed a very significant increase in viscosity of the levitated squalene droplets upon ozonolysis, following their transformation from the liquid to solid phase that was not observable when the oxidation was carried out on coverslip mounted droplets. FLIM imaging with sub-micron spatial resolution also revealed spatial heterogeneity in the viscosity distribution of oxidised droplets. Overall, a combination of molecular rotors, FLIM and optical trapping is able to provide powerful insights into OA chemistry and the microscopic structure that enables the dynamic monitoring of microscopic viscosity in aerosol particles in their true phase.

Mixotrophy drives niche expansion of verrucomicrobial methanotrophs

PubMed Central

Carere, Carlo R; Hards, Kiel; Houghton, Karen M; Power, Jean F; McDonald, Ben; Collet, Christophe; Gapes, Daniel J; Sparling, Richard; Boyd, Eric S; Cook, Gregory M; Greening, Chris; Stott, Matthew B

2017-01-01

Aerobic methanotrophic bacteria have evolved a specialist lifestyle dependent on consumption of methane and other short-chain carbon compounds. However, their apparent substrate specialism runs contrary to the high relative abundance of these microorganisms in dynamic environments, where the availability of methane and oxygen fluctuates. In this work, we provide in situ and ex situ evidence that verrucomicrobial methanotrophs are mixotrophs. Verrucomicrobia-dominated soil communities from an acidic geothermal field in Rotokawa, New Zealand rapidly oxidised methane and hydrogen simultaneously. We isolated and characterised a verrucomicrobial strain from these soils, Methylacidiphilum sp. RTK17.1, and showed that it constitutively oxidises molecular hydrogen. Genomic analysis confirmed that this strain encoded two [NiFe]-hydrogenases (group 1d and 3b), and biochemical assays revealed that it used hydrogen as an electron donor for aerobic respiration and carbon fixation. While the strain could grow heterotrophically on methane or autotrophically on hydrogen, it grew optimally by combining these metabolic strategies. Hydrogen oxidation was particularly important for adaptation to methane and oxygen limitation. Complementary to recent findings of hydrogenotrophic growth by Methylacidiphilum fumariolicum SolV, our findings illustrate that verrucomicrobial methanotrophs have evolved to simultaneously utilise hydrogen and methane from geothermal sources to meet energy and carbon demands where nutrient flux is dynamic. This mixotrophic lifestyle is likely to have facilitated expansion of the niche space occupied by these microorganisms, allowing them to become dominant in geothermally influenced surface soils. Genes encoding putative oxygen-tolerant uptake [NiFe]-hydrogenases were identified in all publicly available methanotroph genomes, suggesting hydrogen oxidation is a general metabolic strategy in this guild. PMID:28777381

Iron-montmorillonite clays as active sorbents for the decontamination of hazardous chemical warfare agents.

PubMed

Carniato, F; Bisio, C; Evangelisti, C; Psaro, R; Dal Santo, V; Costenaro, D; Marchese, L; Guidotti, M

2018-02-27

A class of heterogeneous catalysts based on commercial bentonite from natural origin, containing at least 80 wt% of montmorillonite clay, was designed to transform selectively and under mild conditions toxic organosulfur and organophosphorus chemical warfare agents into non-noxious products with a reduced impact on health and environment. The bentonite from the natural origin was modified by introducing iron species and acid sites in the interlayer space, aiming to obtain a sorbent with strong catalytic oxidising and hydrolytic properties. The catalytic performance of these materials was evaluated in the oxidative abatement of (2-chloroethyl)ethyl sulfide (CEES), a simulant of sulfur mustard, in the presence of aqueous hydrogen peroxide as an oxidant. A new decontamination formulation was, moreover, proposed and obtained by mixing sodium perborate, as a solid oxidant, to iron-bentonite catalysts. Solid-phase decontamination tests, performed on a cotton textile support contaminated with organosulfide and organophosphonate simulant agents revealed the good activity of the solid formulation, especially in the in situ detoxification of blistering agents. Tests carried out on the real blistering warfare agent, sulfur mustard (HD agent), showed that, thanks to the co-presence of the iron-based clay together with the solid oxidant component, a good decontamination of the test surface from the real warfare agent could be achieved (80% contaminant degradation, under ambient conditions, in 24 h).

Arsenic incorporation into FeS 2 pyrite and its influence on dissolution: A DFT study

NASA Astrophysics Data System (ADS)

Blanchard, Marc; Alfredsson, Maria; Brodholt, John; Wright, Kate; Catlow, C. Richard A.

2007-02-01

FeS 2 pyrite can incorporate large amounts of arsenic (up to ca. 10 wt%) and hence has a strong impact on the mobility of this toxic metalloid. Focussing on the lowest arsenic concentrations for which the incorporation occurs in solid solution, the substitution mechanisms involved have been investigated by assuming simple incorporation reactions in both oxidising and reducing conditions. The solution energies were calculated by Density Functional Theory (DFT) calculations and we predict that the formation of AsS dianion groups is the most energetically favourable mechanism. The results also suggest that the presence of arsenic will accelerate the dissolution and thus the generation of acid drainage, when the crystal dissolves in oxidising conditions.

Unravelling the Carbon and Sulphur Metabolism in Coastal Soil Ecosystems Using Comparative Cultivation-Independent Genome-Level Characterisation of Microbial Communities

PubMed Central

Yousuf, Basit; Kumar, Raghawendra; Mishra, Avinash; Jha, Bhavanath

2014-01-01

Bacterial autotrophy contributes significantly to the overall carbon balance, which stabilises atmospheric CO2 concentration and decelerates global warming. Little attention has been paid to different modes of carbon/sulphur metabolism mediated by autotrophic bacterial communities in terrestrial soil ecosystems. We studied these pathways by analysing the distribution and abundance of the diagnostic metabolic marker genes cbbM, apsA and soxB, which encode for ribulose-1,5-bisphosphate carboxylase/oxygenase, adenosine phosphosulphate reductase and sulphate thiohydrolase, respectively, among different contrasting soil types. Additionally, the abundance of community members was assessed by quantifying the gene copy numbers for 16S rRNA, cbbL, cbbM, apsA and soxB. Distinct compositional differences were observed among the clone libraries, which revealed a dominance of phylotypes associated with carbon and sulphur cycling, such as Gammaproteobacteria (Thiohalomonas, Allochromatium, Chromatium, Thiomicrospira) and Alphaproteobacteria (Rhodopseudomonas, Rhodovulum, Paracoccus). The rhizosphere soil was devoid of sulphur metabolism, as the soxB and apsA genes were not observed in the rhizosphere metagenome, which suggests the absence or inadequate representation of sulphur-oxidising bacteria. We hypothesise that the novel Gammaproteobacteria sulphur oxidisers might be actively involved in sulphur oxidation and inorganic carbon fixation, particularly in barren saline soil ecosystems, suggesting their significant putative ecological role and contribution to the soil carbon pool. PMID:25225969

Unravelling the carbon and sulphur metabolism in coastal soil ecosystems using comparative cultivation-independent genome-level characterisation of microbial communities.

PubMed

Yousuf, Basit; Kumar, Raghawendra; Mishra, Avinash; Jha, Bhavanath

2014-01-01

Bacterial autotrophy contributes significantly to the overall carbon balance, which stabilises atmospheric CO2 concentration and decelerates global warming. Little attention has been paid to different modes of carbon/sulphur metabolism mediated by autotrophic bacterial communities in terrestrial soil ecosystems. We studied these pathways by analysing the distribution and abundance of the diagnostic metabolic marker genes cbbM, apsA and soxB, which encode for ribulose-1,5-bisphosphate carboxylase/oxygenase, adenosine phosphosulphate reductase and sulphate thiohydrolase, respectively, among different contrasting soil types. Additionally, the abundance of community members was assessed by quantifying the gene copy numbers for 16S rRNA, cbbL, cbbM, apsA and soxB. Distinct compositional differences were observed among the clone libraries, which revealed a dominance of phylotypes associated with carbon and sulphur cycling, such as Gammaproteobacteria (Thiohalomonas, Allochromatium, Chromatium, Thiomicrospira) and Alphaproteobacteria (Rhodopseudomonas, Rhodovulum, Paracoccus). The rhizosphere soil was devoid of sulphur metabolism, as the soxB and apsA genes were not observed in the rhizosphere metagenome, which suggests the absence or inadequate representation of sulphur-oxidising bacteria. We hypothesise that the novel Gammaproteobacteria sulphur oxidisers might be actively involved in sulphur oxidation and inorganic carbon fixation, particularly in barren saline soil ecosystems, suggesting their significant putative ecological role and contribution to the soil carbon pool.

Chemical surface alteration of biodegradable magnesium exposed to corrosion media.

PubMed

Willumeit, Regine; Fischer, Janine; Feyerabend, Frank; Hort, Norbert; Bismayer, Ulrich; Heidrich, Stefanie; Mihailova, Boriana

2011-06-01

The understanding of corrosion processes of metal implants in the human body is a key problem in modern biomaterial science. Because of the complicated and adjustable in vivo environment, in vitro experiments require the analysis of various physiological corrosion media to elucidate the underlying mechanism of "biological" metal surface modification. In this paper magnesium samples were incubated under cell culture conditions (i.e. including CO(2)) in electrolyte solutions and cell growth media, with and without proteins. Chemical mapping by high-resolution electron-induced X-ray emission spectroscopy and infrared reflection microspectroscopy revealed a complex structure of the formed corrosion layer. The presence of CO(2) in concentrations close to that in blood is significant for the chemistry of the oxidised layer. The presence of proteins leads to a less dense but thicker passivation layer which is still ion and water permeable, as osmolality and weight measurements indicate. Copyright © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Facile oxidation of leucomethylene blue and dihydroflavins by artemisinins: relationship with flavoenzyme function and antimalarial mechanism of action.

PubMed

Haynes, Richard K; Chan, Wing-Chi; Wong, Ho-Ning; Li, Ka-Yan; Wu, Wai-Keung; Fan, Kit-Man; Sung, Herman H Y; Williams, Ian D; Prosperi, Davide; Melato, Sergio; Coghi, Paolo; Monti, Diego

2010-08-02

The antimalarial drug methylene blue (MB) affects the redox behaviour of parasite flavin-dependent disulfide reductases such as glutathione reductase (GR) that control oxidative stress in the malaria parasite. The reduced flavin adenine dinucleotide cofactor FADH(2) initiates reduction to leucomethylene blue (LMB), which is oxidised by oxygen to generate reactive oxygen species (ROS) and MB. MB then acts as a subversive substrate for NADPH normally required to regenerate FADH(2) for enzyme function. The synergism between MB and the peroxidic antimalarial artemisinin derivative artesunate suggests that artemisinins have a complementary mode of action. We find that artemisinins are transformed by LMB generated from MB and ascorbic acid (AA) or N-benzyldihydronicotinamide (BNAH) in situ in aqueous buffer at physiological pH into single electron transfer (SET) rearrangement products or two-electron reduction products, the latter of which dominates with BNAH. Neither AA nor BNAH alone affects the artemisinins. The AA-MB SET reactions are enhanced under aerobic conditions, and the major products obtained here are structurally closely related to one such product already reported to form in an intracellular medium. A ketyl arising via SET with the artemisinin is invoked to explain their formation. Dihydroflavins generated from riboflavin (RF) and FAD by pretreatment with sodium dithionite are rapidly oxidised by artemisinin to the parent flavins. When catalytic amounts of RF, FAD, and other flavins are reduced in situ by excess BNAH or NAD(P)H in the presence of the artemisinins in the aqueous buffer, they are rapidly oxidised to the parent flavins with concomitant formation of two-electron reduction products from the artemisinins; regeneration of the reduced flavin by excess reductant maintains a catalytic cycle until the artemisinin is consumed. In preliminary experiments, we show that NADPH consumption in yeast GR with redox behaviour similar to that of parasite GR is enhanced by artemisinins, especially under aerobic conditions. Recombinant human GR is not affected. Artemisinins thus may act as antimalarial drugs by perturbing the redox balance within the malaria parasite, both by oxidising FADH(2) in parasite GR or other parasite flavoenzymes, and by initiating autoxidation of the dihydroflavin by oxygen with generation of ROS. Reduction of the artemisinin is proposed to occur via hydride transfer from LMB or the dihydroflavin to O1 of the peroxide. This hitherto unrecorded reactivity profile conforms with known structure-activity relationships of artemisinins, is consistent with their known ability to generate ROS in vivo, and explains the synergism between artemisinins and redox-active antimalarial drugs such as MB and doxorubicin. As the artemisinins appear to be relatively inert towards human GR, a putative model that accounts for the selective potency of artemisinins towards the malaria parasite also becomes apparent. Decisively, ferrous iron or carbon-centered free radicals cannot be involved, and the reactivity described herein reconciles disparate observations that are incompatible with the ferrous iron-carbon radical hypothesis for antimalarial mechanism of action. Finally, the urgent enquiry into the emerging resistance of the malaria parasite to artemisinins may now in one part address the possibilities either of structural changes taking place in parasite flavoenzymes that render the flavin cofactor less accessible to artemisinins or of an enhancement in the ability to use intra-erythrocytic human disulfide reductases required for maintenance of parasite redox balance.

Isolation and characterisation of mineral-oxidising "Acidibacillus" spp. from mine sites and geothermal environments in different global locations.

PubMed

Holanda, Roseanne; Hedrich, Sabrina; Ňancucheo, Ivan; Oliveira, Guilherme; Grail, Barry M; Johnson, D Barrie

2016-09-01

Eight strains of acidophilic bacteria, isolated from mine-impacted and geothermal sites from different parts of the world, were shown to form a distinct clade (proposed genus "Acidibacillus") within the phylum Firmicutes, well separated from the acidophilic genera Sulfobacillus and Alicyclobacillus. Two of the strains (both isolated from sites in Yellowstone National Park, USA) were moderate thermophiles that oxidised both ferrous iron and elemental sulphur, while the other six were mesophiles that also oxidised ferrous iron, but not sulphur. All eight isolates reduced ferric iron to varying degrees. The two groups shared <95% similarity of their 16S rRNA genes and were therefore considered to be distinct species: "Acidibacillus sulfuroxidans" (moderately thermophilic isolates) and "Acidibacillus ferrooxidans" (mesophilic isolates). Both species were obligate heterotrophs; none of the eight strains grew in the absence of organic carbon. "Acidibacillus" spp. were generally highly tolerant of elevated concentrations of cationic transition metals, though "A. sulfuroxidans" strains were more sensitive to some (e.g. nickel and zinc) than those of "A. ferrooxidans". Initial annotation of the genomes of two strains of "A. ferrooxidans" revealed the presence of genes (cbbL) involved in the RuBisCO pathway for CO2 assimilation and iron oxidation (rus), though with relatively low sequence identities. Copyright © 2016. Published by Elsevier Masson SAS.

An Investigation on the Persistence of Uranium Hydride during Storage of Simulant Nuclear Waste Packages.

PubMed

Stitt, C A; Harker, N J; Hallam, K R; Paraskevoulakos, C; Banos, A; Rennie, S; Jowsey, J; Scott, T B

2015-01-01

Synchrotron X-rays have been used to study the oxidation of uranium and uranium hydride when encapsulated in grout and stored in de-ionised water for 10 months. Periodic synchrotron X-ray tomography and X-ray powder diffraction have allowed measurement and identification of the arising corrosion products and the rates of corrosion. The oxidation rates of the uranium metal and uranium hydride were slower than empirically derived rates previously reported for each reactant in an anoxic water system, but without encapsulation in grout. This was attributed to the grout acting as a physical barrier limiting the access of oxidising species to the uranium surface. Uranium hydride was observed to persist throughout the 10 month storage period and industrial consequences of this observed persistence are discussed.

Ultramicroelectrode voltammetry and scanning electrochemical microscopy in room-temperature ionic liquid electrolytes.

PubMed

Walsh, Darren A; Lovelock, Kevin R J; Licence, Peter

2010-11-01

The high viscosity and unusual properties of room temperature ionic liquids (RTILs) present a number of challenges when performing steady-state voltammetry and scanning electrochemical microscopy in RTILs. These include difficulties in recording steady-state currents at ultramicroelectrode surfaces due to low diffusion coefficients of redox species and problems associated with unequal diffusion coefficients of oxidised and reduced species in RTILs. In this tutorial review, we highlight the recent progress in the use of RTILs as electrolytes for ultramicroelectrode voltammetry and SECM. We describe the basic principles of ultramicroelectrode voltammetry and SECM and, using examples from the recent literature, we discuss the conditions that must be met to perform steady-state voltammetry and SECM measurements in RTILs. Finally, we briefly discuss the electrochemical insights that can be obtained from such measurements.

Investigation of the aluminium-aluminium oxide reversible transformation as observed by hot stage electron microscopy.

NASA Technical Reports Server (NTRS)

Grove, C. A.; Judd, G.; Ansell, G. S.

1972-01-01

Thin foils of high purity aluminium and an Al-Al2O3 SAP type of alloy were oxidised in a specially designed hot stage specimen chamber in an electron microscope. Below 450 C, amorphous aluminium oxide formed on the foil surface and was first detectable at foil edges, holes, and pits. Islands of aluminium then nucleated in this amorphous oxide. The aluminium islands displayed either a lateral growth with eventual coalescence with other islands, or a reoxidation process which caused the islands to disappear. The aluminium island formation was determined to be related to the presence of the electron beam. A mechanism based upon electron charging due to the electron beam was proposed to explain the nucleation, growth, coalescence, disappearance, and geometry of the aluminium islands.

An Investigation on the Persistence of Uranium Hydride during Storage of Simulant Nuclear Waste Packages

PubMed Central

Harker, N. J.; Hallam, K. R.; Paraskevoulakos, C.; Banos, A.; Rennie, S.; Jowsey, J.

2015-01-01

Synchrotron X-rays have been used to study the oxidation of uranium and uranium hydride when encapsulated in grout and stored in de-ionised water for 10 months. Periodic synchrotron X-ray tomography and X-ray powder diffraction have allowed measurement and identification of the arising corrosion products and the rates of corrosion. The oxidation rates of the uranium metal and uranium hydride were slower than empirically derived rates previously reported for each reactant in an anoxic water system, but without encapsulation in grout. This was attributed to the grout acting as a physical barrier limiting the access of oxidising species to the uranium surface. Uranium hydride was observed to persist throughout the 10 month storage period and industrial consequences of this observed persistence are discussed. PMID:26176551

The Impact of Potassium Manganate (VII) on the Effectiveness of Coagulation in the Removal of Iron and Manganese from Groundwater with an Increased Content of Organic Substances

NASA Astrophysics Data System (ADS)

Krupińska, Izabela

2017-12-01

The article presents the results of studies concerning the impact of the method of Fe(II) ion oxidisation (dissolved oxygen and potassium manganate (VII)) on the effectiveness of coagulation in the removal of iron and manganese from groundwater with an increased content of organic substances. The efficiencies of two coagulants were compared: aluminium sulphate (VI) and polyaluminium chloride (Flokor 1.2A). Among the used methods of iron (II) oxidisation, the best effects have been achieved by potassium manganate (VII) because one of the oxidation products was manganese oxide (IV) precipitating from water. Better results in purifying the water were obtained with the use of a prehydrolysed coagulant Flokor 1.2 A than aluminium sulphate (VI).

Oxidative stress biomarkers in two resident species, mullet (Mugil cephalus) and flounder (Platichthys flesus), from a polluted site in River Douro Estuary, Portugal.

PubMed

Ferreira, M; Moradas-Ferreira, P; Reis-Henriques, M A

2005-01-18

Exposure of marine animals to certain pollutants can enhance reactive oxygen species (ROS) production with subsequent damage to macromolecules and alterations in oxidant defences levels. Aimed at correlating the tissue concentration of certain contaminants (PCBs, DDT) with antioxidant defence levels and oxidative damages, two fish species with different life strategies (mullet, Mugil cephalus, and flounder, Platichthys flesus) were collected in the Douro Estuary (NW Portugal). After capture, the fish were left to depurate for 1 month in clean seawater. The levels of the two antioxidant enzyme activities revealed that they are species-dependent with mullet's livers showing higher superoxide dismutase (SOD) (13.2+/-0.5 U/mg protein) and catalase (CAT) (15.5+/-1.0 mmol/min/mg protein) activities than flounder (SOD: 7.9+/-0.9 U/mg protein; CAT: 11.1+/-0.8 mmol/min/mg protein). After 1 month in captivity the antioxidant enzymes activities in liver decreased in mullets, while for flounders the responses were not consistent because during the experimental period flounders did not ate and responses of antioxidant enzymes and oxidative damages were dependent on the fasting condition. The liver oxidative damages were evaluated by estimating oxidised lipids and proteins. Both species showed similar levels for these two parameters. The hepatic lipid peroxidation in flounder increased after 1 month in captivity, while in mullet an increase was observed only in summer and autumn. The oxidised protein content increased for both species after the depuration period. This study reveals differences between species under oxidative stress when exposed to pollutants. In a clean environment, the mullet's primary antioxidant defences decreased indicating that the animals living in Douro estuary were facing an oxidative stress. The data indicate that, namely in mullet, the presence of pollutants induce oxidative stress responses.

Effect of wet oxidation on the fingerprints of polymeric substances from an activated sludge.

PubMed

Urrea, José Luis; Collado, Sergio; Oulego, Paula; Díaz, Mario

2016-11-15

Thermal pre-treatments of activated sludge involve the release of a high amount of polymeric substances into the bulk medium. The molecular size of these polymers will largely define the subsequent biological treatment of the liquid effluent generated. In this work, the effects of wet oxidation treatment (WO) on the fingerprints of the polymeric substances which compose the activated sludge, were analysed. For a better understanding of these transformations, the sludge was separated into its main fractions: soluble microbial products (SMP), loosely bound extracellular polymeric substances (LB-EPS), tightly bound extracellular polymeric substances (TB-EPS) and naked cells, and then each one was subjected to WO separately (190 °C and 65 bar), determining the fingerprints evolution by size exclusion technique. Results revealed a fast degradation of larger molecules (over 500 kDa) during the first minutes of treatment (40 min). WO also increases the absorptive properties of proteins (especially for 30 kDa), which is possibly due to the hydroxylation of phenylalanine amino acids in their structure. WO of naked cells involved the formation of molecules between 23 and 190 kDa, which are related to the release of cytoplasmic polymers, and more hydrophobic polymers, probably from the cell membrane. The results allowed to establish a relationship between the location of polymeric material and its facility to become oxidised; thus, the more internal the polymeric material in the cell, the easier its oxidation. When working directly with the raw sludge, hydrolysis mechanisms played a key role during the starting period. Once a high degree of solubilisation was reached, the molecules were rapidly oxidised into other compounds with refractory characteristics. The final effluent after WO showed almost 90% of low molecular weight solubilised substances (0-35 kDa). Copyright © 2016 Elsevier Ltd. All rights reserved.

Photo-oxidation of tyrosine in a bio-engineered bacterioferritin 'reaction centre'-a protein model for artificial photosynthesis.

PubMed

Hingorani, Kastoori; Pace, Ron; Whitney, Spencer; Murray, James W; Smith, Paul; Cheah, Mun Hon; Wydrzynski, Tom; Hillier, Warwick

2014-10-01

The photosynthetic reaction centre (RC) is central to the conversion of solar energy into chemical energy and is a model for bio-mimetic engineering approaches to this end. We describe bio-engineering of a Photosystem II (PSII) RC inspired peptide model, building on our earlier studies. A non-photosynthetic haem containing bacterioferritin (BFR) from Escherichia coli that expresses as a homodimer was used as a protein scaffold, incorporating redox-active cofactors mimicking those of PSII. Desirable properties include: a di-nuclear metal binding site which provides ligands for bivalent metals, a hydrophobic pocket at the dimer interface which can bind a photosensitive porphyrin and presence of tyrosine residues proximal to the bound cofactors, which can be utilised as efficient electron-tunnelling intermediates. Light-induced electron transfer from proximal tyrosine residues to the photo-oxidised ZnCe6(•+), in the modified BFR reconstituted with both ZnCe6 and Mn(II), is presented. Three site-specific tyrosine variants (Y25F, Y58F and Y45F) were made to localise the redox-active tyrosine in the engineered system. The results indicate that: presence of bound Mn(II) is necessary to observe tyrosine oxidation in all BFR variants; Y45 the most important tyrosine as an immediate electron donor to the oxidised ZnCe6(•+) and that Y25 and Y58 are both redox-active in this system, but appear to function interchangebaly. High-resolution (2.1Å) crystal structures of the tyrosine variants show that there are no mutation-induced effects on the overall 3-D structure of the protein. Small effects are observed in the Y45F variant. Here, the BFR-RC represents a protein model for artificial photosynthesis. Crown Copyright © 2014. Published by Elsevier B.V. All rights reserved.

Microplasma array patterning of reactive oxygen and nitrogen species onto polystyrene

NASA Astrophysics Data System (ADS)

Szili, Endre J.; Dedrick, James; Oh, Jun-Seok; Bradley, James W.; Boswell, Roderick W.; Charles, Christine; Short, Robert D.; Al-Bataineh, Sameer A.

2017-02-01

We investigate an approach for the patterning of reactive oxygen and nitrogen species (RONS) onto polystyrene using atmospheric-pressure microplasma arrays. The spectrally integrated and time-resolved optical emission from the array is characterised with respect to the applied voltage, applied-voltage frequency and pressure; and the array is used to achieve spatially resolved modification of polystyrene at three pressures: 500 Torr, 760 Torr and 1000 Torr. As determined by time-of-flight secondary ion mass spectrometry (ToF-SIMS), regions over which surface modification occurs are clearly restricted to areas that are exposed to individual microplasma cavities. Analysis of the negative-ion ToF-SIMS mass spectra from the centre of the modified microspots shows that the level of oxidation is dependent on the operating pressure, and closely correlated with the spatial distribution of the optical emission. The functional groups that are generated by the microplasma array on the polystyrene surface are shown to readily participate in an oxidative reaction in phosphate buffered saline solution (pH 7.4). Patterns of oxidised and chemically reactive functionalities could potentially be applied to the future development of biomaterial surfaces, where spatial control over biomolecule or cell function is needed.

Porous silicon nanocrystals in a silica aerogel matrix

PubMed Central

2012-01-01

Silicon nanoparticles of three types (oxide-terminated silicon nanospheres, micron-sized hydrogen-terminated porous silicon grains and micron-size oxide-terminated porous silicon grains) were incorporated into silica aerogels at the gel preparation stage. Samples with a wide range of concentrations were prepared, resulting in aerogels that were translucent (but weakly coloured) through to completely opaque for visible light over sample thicknesses of several millimetres. The photoluminescence of these composite materials and of silica aerogel without silicon inclusions was studied in vacuum and in the presence of molecular oxygen in order to determine whether there is any evidence for non-radiative energy transfer from the silicon triplet exciton state to molecular oxygen adsorbed at the silicon surface. No sensitivity to oxygen was observed from the nanoparticles which had partially H-terminated surfaces before incorporation, and so we conclude that the silicon surface has become substantially oxidised. Finally, the FTIR and Raman scattering spectra of the composites were studied in order to establish the presence of crystalline silicon; by taking the ratio of intensities of the silicon and aerogel Raman bands, we were able to obtain a quantitative measure of the silicon nanoparticle concentration independent of the degree of optical attenuation. PMID:22805684

Porous silicon nanocrystals in a silica aerogel matrix.

PubMed

Amonkosolpan, Jamaree; Wolverson, Daniel; Goller, Bernhard; Polisski, Sergej; Kovalev, Dmitry; Rollings, Matthew; Grogan, Michael D W; Birks, Timothy A

2012-07-17

Silicon nanoparticles of three types (oxide-terminated silicon nanospheres, micron-sized hydrogen-terminated porous silicon grains and micron-size oxide-terminated porous silicon grains) were incorporated into silica aerogels at the gel preparation stage. Samples with a wide range of concentrations were prepared, resulting in aerogels that were translucent (but weakly coloured) through to completely opaque for visible light over sample thicknesses of several millimetres. The photoluminescence of these composite materials and of silica aerogel without silicon inclusions was studied in vacuum and in the presence of molecular oxygen in order to determine whether there is any evidence for non-radiative energy transfer from the silicon triplet exciton state to molecular oxygen adsorbed at the silicon surface. No sensitivity to oxygen was observed from the nanoparticles which had partially H-terminated surfaces before incorporation, and so we conclude that the silicon surface has become substantially oxidised. Finally, the FTIR and Raman scattering spectra of the composites were studied in order to establish the presence of crystalline silicon; by taking the ratio of intensities of the silicon and aerogel Raman bands, we were able to obtain a quantitative measure of the silicon nanoparticle concentration independent of the degree of optical attenuation.

Acidification of lake water due to drought

NASA Astrophysics Data System (ADS)

Mosley, L. M.; Zammit, B.; Jolley, A. M.; Barnett, L.

2014-04-01

Droughts are predicted to increase in many river systems due to increased demand on water resources and climate variability. A severe drought in the Murray-Darling Basin of Australia from 2007 to 2009 resulted in unprecedented declines in water levels in the Lower Lakes (Ramsar-listed ecosystem of international importance) at the end of the river system. The receding water exposed large areas (>200 km2) of sediments on the lake margins. The pyrite (FeS2) in these sediments oxidised and generated high concentrations of acidity. Upon rewetting of the exposed sediments, by rainfall or lake refill, surface water acidification (pH 2-3) occurred in several locations (total area of 21.7 km2). High concentrations of dissolved metals (Al, As, Co, Cr, Cu, Fe, Mn, Ni, Zn), which greatly exceeded aquatic ecosystem protection guidelines, were mobilised in the acidic conditions. In many areas neutralisation of the surface water acidity occurred naturally during lake refill, but aerial limestone dosing was required in two areas to assist in restoring alkalinity. However acidity persists in the submerged lake sediment and groundwater several years after surface water neutralisation. The surface water acidification proved costly to manage and improved water management in the Murray-Darling Basin is required to prevent similar events occurring in the future.

Partially oxidised organic components in urban aerosol using GCXGC-TOF/MS

NASA Astrophysics Data System (ADS)

Hamilton, J. F.; Webb, P. J.; Lewis, A. C.; Hopkins, J. R.; Smith, S.; Davy, P.

2004-08-01

Partially oxidised organic compounds associated with PM2.5 aerosol collected in London, England, have been analysed using direct thermal desorption coupled to comprehensive gas chromatography-time of flight mass spectrometry (GCXGC-TOF/MS). Over 10000 individual organic components were isolated from around 10µg of aerosol material in a single procedure and with no sample pre-treatment. Chemical functionalities observed using this analytical technique ranged from alkanes to poly-oxygenated species. The chemical band structures commonly used in GCXGC for group type identifications overlap for this sample type, and have required mass spectrometry as an additional level of instrument dimensionality. An investigation of oxygenated volatile organic compounds (o-VOC) contained within urban aerosol has been performed and in a typical sample around 130 o-VOCs were identified based on retention behaviour and spectral match. In excess of 100 other oxygenated species were also observed but lack of mass spectral library or pure components prevents positive identification. Many of the carbonyl species observed could be mechanistically linked to gas phase aromatic hydrocarbon oxidation and there is good agreement in terms of speciation between the urban samples analysed here and those degradation products observed in smog chamber experiments of aromatic oxidation. The presence of partially oxidised species such as linear chain aldehydes and ketones and cyclic products such as furanones suggests that species generated early in the oxidative process may undergo gas to particle partitioning despite their relatively high volatility.

Partially oxidised organic components in urban aerosol using GCXGC-TOF/MS

NASA Astrophysics Data System (ADS)

Hamilton, J.; Webb, P.; Lewis, A.; Hopkins, J.; Smith, S.; Davy, P.

2004-03-01

Partially oxidised organic compounds associated with PM2.5 aerosol collected in London, England, have been analysed using direct thermal desorption coupled to comprehensive gas chromatography-time of flight mass spectrometry (GCXGC-OF/MS). Over 10 000 individual organic components were isolated from around 10 μg of aerosol material in a single procedure and with no sample pre-treatment. Chemical functionalities observed using this analytical technique ranged from alkanes to poly-oxygenated species. The chemical band structures commonly used in GCXGC for group type identifications overlap for this sample type, and have required mass spectrometry as an additional level of instrument dimensionality. An investigation of oxygenated volatile organic compounds (o-VOC) contained within urban aerosol has been performed and in a typical sample around 130 o-VOCs were identified based on retention behaviour and spectral match. In excess of 100 other oxygenated species were also observed but lack of mass spectral library or pure components prevents positive identification. Many of the carbonyl species observed could be mechanistically linked to gas phase aromatic hydrocarbon oxidation and there is good agreement in terms of speciation between the urban samples analysed here and those degradation products observed in smog chamber experiments of aromatic oxidation. The presence of partially oxidised species such as linear chain aldehydes and ketones and cyclic products such as furanones suggests that species generated relatively early in the oxidative process may undergo gas to particle partitioning despite their relatively high volatility.

Lemon grass (Cymbopogon citratus (D.C) Stapf) polyphenols protect human umbilical vein endothelial cell (HUVECs) from oxidative damage induced by high glucose, hydrogen peroxide and oxidised low-density lipoprotein.

PubMed

Campos, J; Schmeda-Hirschmann, G; Leiva, E; Guzmán, L; Orrego, R; Fernández, P; González, M; Radojkovic, C; Zuñiga, F A; Lamperti, L; Pastene, E; Aguayo, C

2014-05-15

The aromatic herb Cymbopogon citratus Stapf is widely used in tropical and subtropical countries in cooking, as a herbal tea, and in traditional medicine for hypertension and diabetes. Some of its properties have been associated with the in vitro antioxidant effect of polyphenols isolated from their aerial parts. However, little is known about C. citratus effects on endothelial cells oxidative injury. Using chromatographic procedures, a polyphenol-rich fraction was obtained from C. citratus (CCF) and their antioxidant properties were assessed by cooper-induced LDL oxidation assay. The main constituents of the active CCF, identified by high-performance liquid chromatography with diode-array detection and mass spectrometry (HPLC-DAD-MS), were chlorogenic acid, isoorientin and swertiajaponin. CCF 10 and 100 μg/ml diminishes reactive oxidative species (ROS) production in human umbilical vein endothelial cell (HUVECs), challenged with high D-glucose (60% inhibition), hydrogen peroxide (80% inhibition) or oxidised low-density lipoprotein (55% inhibition). CCF 10 or 100 μg/ml did not change nitric oxide (NO) production. However, CCF was able to inhibit vasoconstriction induced by the thromboxane A2 receptor agonist U46619, which suggest a NO-independent vasodilatador effect on blood vessels. Our results suggest that lemon grass antioxidant properties might prevent endothelial dysfunction associated to an oxidative imbalance promoted by different oxidative stimuli. Copyright © 2013 Elsevier Ltd. All rights reserved.

Vanguard: a Mars exobiology mission proposal using robotic elements

NASA Astrophysics Data System (ADS)

Ellery, A.; Richter, L.; Kolb, C.; Lammer, H.; Parnell, J.; Bertrand, R.; Ball, A.; Patel, M.; Coste, P.; McKee, G.

2003-04-01

We present a new proposal for a European exobiology-focussed robotic Mars mission. This mission is presented as a low-cost successor to the Mars Express/Beagle2 mission. The Mars surface segment is designed within the payload constraints of the current Mars Express bus spacecraft with a mass of 126 kg including the Entry, Descent and Landing System (EDLS). EDLS will be similar to that employed for Beagle2 and Mars Pathfinder. The surface segment will have a total mass of 66 kg including a 34 kg lander, a 26 kg micro-rover and three 1.6 kg moles. The exobiology focus requires that investigation of the Martian sub-surface, below the oxidised layer, be undertaken in search of biomolecular species. The currently favoured site for deployment is the Gusev palaeolake crater. The moles are mounted vertically to the rear of the micro-rover which will enable a surface traverse of 1-5 km. Each molewill be deployed sequentially at different sites selected during the mission operation. Each mole will penetrate below the projected depth of the oxidised layer (estimated at 2-3m depth) to a total depth of 5m. The micro-rover will carry the main scientific instrument pack of a combined confocal imager, Raman spectrometer, infrared spectrometer and laser plasma spectrometer. Each of these instruments enables remote sensing of mineralogy, elemental abundance, biomolecules and water signatures with depth. The implementation of a dedicated tether to each mole from the micro-rover provides the provision of power and optical fibre links from the instruments to the sub-surface targets. As remote sensing instruments, there is no requirement for the recovery of physical samples, eliminating much of the complexity inherent in recovering the moles. Each mole is thus deployed on a single one-way trajectory to maximum depth on which the tether is severed. A minimum of three moles is considered essential in providing replicated depth profile data sets. Furthermore, the mission has a specific technology demonstration component to it in providing a basic demonstration of water-mining as part of an in-situ resource utilisation validation programme - this will be achieved using zeolite caps deployed at the top of each borehole. There are a number of robotics issues inherent in this proposal. First, the micro-rover traverse requires extensive onboard navigation capabilities - we are investigating the use of the elastic loop mobility system for surface negotiation and potential fields as the mode of near-autonomous navigation. Second, the single direction mole trajectory will require a sophisticated onboard expert system to quick-look analyse depth profile data to make decisions on the control of the mole. The Vanguard mission represents a low-cost robotic Mars mission with a high scientific return and a significant demonstration of robotic technologies required for future Mars missions. We are currently proposing Vanguard as an Aurora Arrow mission to complement the Aurora ExoMars flagship mission.

Membrane chemical reactor (MCR) combining photocatalysis and microfiltration for grey water treatment.

PubMed

Rivero, M J; Parsons, S A; Jeffrey, P; Pidou, M; Jefferson, B

2006-01-01

Urban water recycling is now becoming an important issue where water resources are becoming scarce. This paper looks at reusing grey water; the preference is treatment processes based on biological systems to remove the dissolved organic content. Here, an alternative process, photocatalysis is discussed as it is an attractive technology that could be well-suited for treating the recalcitrant organic compounds found in grey water. The photocatalytic process oxidises organic reactants at a catalyst surface in the presence of ultraviolet light. Given enough exposure time, organic compounds will be oxidized into CO2 and water. The best contact is achieved in a slurry reactor but a second step to separate and recover the catalyst is need. This paper discusses a new membrane chemical reactor (MCR) combining photocatalysis and microfiltration for grey water treatment.

Photo-Oxidation Products of Skin Surface Squalene Mediate Metabolic and Inflammatory Responses to Solar UV in Human Keratinocytes

PubMed Central

Kostyuk, Vladimir; Potapovich, Alla; Stancato, Andrea; De Luca, Chiara; Lulli, Daniela; Pastore, Saveria; Korkina, Liudmila

2012-01-01

The study aimed to identify endogenous lipid mediators of metabolic and inflammatory responses of human keratinocytes to solar UV irradiation. Physiologically relevant doses of solar simulated UVA+UVB were applied to human skin surface lipids (SSL) or to primary cultures of normal human epidermal keratinocytes (NHEK). The decay of photo-sensitive lipid-soluble components, alpha-tocopherol, squalene (Sq), and cholesterol in SSL was analysed and products of squalene photo-oxidation (SqPx) were quantitatively isolated from irradiated SSL. When administered directly to NHEK, low-dose solar UVA+UVB induced time-dependent inflammatory and metabolic responses. To mimic UVA+UVB action, NHEK were exposed to intact or photo-oxidised SSL, Sq or SqPx, 4-hydroxy-2-nonenal (4-HNE), and the product of tryptophan photo-oxidation 6-formylindolo[3,2-b]carbazole (FICZ). FICZ activated exclusively metabolic responses characteristic for UV, i.e. the aryl hydrocarbon receptor (AhR) machinery and downstream CYP1A1/CYP1B1 gene expression, while 4-HNE slightly stimulated inflammatory UV markers IL-6, COX-2, and iNOS genes. On contrast, SqPx induced the majority of metabolic and inflammatory responses characteristic for UVA+UVB, acting via AhR, EGFR, and G-protein-coupled arachidonic acid receptor (G2A). Conclusions/Significance Our findings indicate that Sq could be a primary sensor of solar UV irradiation in human SSL, and products of its photo-oxidation mediate/induce metabolic and inflammatory responses of keratinocytes to UVA+UVB, which could be relevant for skin inflammation in the sun-exposed oily skin. PMID:22952984

(234)U/(238)U signatures associated with uranium ore bodies: part 3 Koongarra.

PubMed

Lowson, Richard T

2013-04-01

The Koongarra ore body is an early Proterozoic U ore body in the Alligator Rivers U province, Northern Territory, Australia. It has surface expression with a redox front located ∼30 m below the surface. The (234)U/(238)U activity ratios (AR) for the ground water and the amorphous phase of the solid have been analysed for the ore zone and dispersion halo as a function of depth. The results display a (234)U/(238)U AR signature with depth which may be common to all U ore bodies. The (234)U/(238)U AR is depressed below secular equilibrium in the weathered material above the redox front; rises significantly above secular equilibrium in the vicinity of the redox front; and is followed by a gradual decrease with depth below the redox front. The amplitude of the profile is a function of local conditions. A model is proposed for the signature in which oxidising waters preferentially leach the (234)U sites at the redox front due to preconditioning of the (234)U sites by α recoil during the decay of (23)(8)U to (23)(4)U. Mass balance requires the solid material left behind the redox front to have a (234)U/(238)U AR reduced below 1. Local second order effects may be superimposed on the signature. The signature may have application to calibrating scenarios for nuclear waste repositories, assisting in understanding historical climates, economic evaluation of U ore bodies and U exploration. Copyright © 2012 Elsevier Ltd. All rights reserved.

Influence of Pb 2+ ions in the H 2 oxidation on Pt catalyzed hydrogen diffusion anodes in sulfuric acid: presence of oscillatory phenomena

NASA Astrophysics Data System (ADS)

Expósito, E.; Sánchez-Sánchez, C. M.; Solla-Gullón, J.; Montiel, V.

The influence of Pb 2+ ions in sulfuric acid medium on the behavior of a platinum catalyzed hydrogen diffusion electrode (HDE) in a filter press reactor has been studied. A voltammetric study of the H 2 oxidation reaction on a polyoriented platinum electrode and a platinum rotating disk electrode (RDE) in presence of lead ions in solution has also been carried out. Potential oscillations were found in galvanostatic experiments of H 2 oxidation using a HDE catalyzed with platinum when Pb 2+ ions are present in solution. This oscillatory phenomenon was also observed when hydrogen oxidation was carried out in presence of Pb 2+ ions using a platinum RDE. The oscillatory behavior observed has been attributed to an adsorption-oxidation-desorption process of lead on the platinum surface. Due to the low solubility of Pb 2+ in sulfuric acid, at high values of coverage, lead is oxidised to insoluble lead sulfate that blocks the Pt surface. The coupling of the dissolution of lead sulfate and the Pb electrochemical adsorption-oxidation processes cause the oscillatory phenomenon.

U-isotopes and (226)Ra as tracers of hydrogeochemical processes in carbonated karst aquifers from arid areas.

PubMed

Guerrero, José Luis; Vallejos, Ángela; Cerón, Juan Carlos; Sánchez-Martos, Francisco; Pulido-Bosch, Antonio; Bolívar, Juan Pedro

2016-07-01

Sierra de Gádor is a karst macrosystem with a highly complex geometry, located in southeastern Spain. In this arid environment, the main economic activities, agriculture and tourism, are supported by water resources from the Sierra de Gádor aquifer system. The aim of this work was to study the levels and behaviour of some of the most significant natural radionuclides in order to improve the knowledge of the hydrogeochemical processes involved in this groundwater system. For this study, 28 groundwater and 7 surface water samples were collected, and the activity concentrations of the natural U-isotopes ((238)U, (235)U and (234)U) and (226)Ra by alpha spectrometry were determined. The activity concentration of (238)U presented a large variation from around 1.1 to 65 mBq L(-1). Elevated groundwater U concentrations were the result of oxidising conditions that likely promoted U dissolution. The PHREEQC modelling code showed that dissolved U mainly existed as uranyl carbonate complexes. The (234)U/(238)U activity ratios were higher than unity for all samples (1.1-3.8). Additionally, these ratios were in greater disequilibrium in groundwater than surface water samples, the likely result of greater water-rock contact time. (226)Ra presented a wide range of activity concentrations, (0.8 up to about 4 × 10(2) mBq L(-1)); greatest concentrations were detected in the thermal area of Alhama. Most of the samples showed (226)Ra/(234)U activity ratios lower than unity (median = 0.3), likely the result of the greater mobility of U than Ra in the aquifer system. The natural U-isotopes concentrations were strongly correlated with dissolution of sulphate evaporites (mainly gypsum). (226)Ra had a more complex behaviour, showing a strong correlation with water salinity, which was particularly evident in locations where thermal anomalies were detected. The most saline samples showed the lowest (234)U/(238)U activity ratios, probably due to fast uniform bulk mineral dissolution, which would minimize the impact of solubility-controlled fractionation processes. Furthermore, the high bulk dissolution rates promoted greater groundwater (226)Ra/(234)U ratios because the Ra has a comparatively much greater mobility than U in saline conditions. Copyright © 2016 Elsevier Ltd. All rights reserved.

A sulphonated carbon dot-chitosan hybrid hydrogel nanocomposite as an efficient ion-exchange film for Ca2+ and Mg2+ removal

NASA Astrophysics Data System (ADS)

Baruah, Upama; Konwar, Achyut; Chowdhury, Devasish

2016-04-01

We have developed a hybrid hydrogel nanocomposite film via conjugation of oxidised carbon dots synthesized from 11-mercaptoundecanoic acid with chitosan. The potential applicability of the film was then successfully tested for the removal of Ca2+ and Mg2+ ions from solution.We have developed a hybrid hydrogel nanocomposite film via conjugation of oxidised carbon dots synthesized from 11-mercaptoundecanoic acid with chitosan. The potential applicability of the film was then successfully tested for the removal of Ca2+ and Mg2+ ions from solution. Electronic supplementary information (ESI) available: The ESI includes the detailed synthesis and characterization of carbon dots both before and after oxidation and of the carbon dot-chitosan nanocomposite films viz. DLS, SEM, UV-visible, FTIR, PL spectroscopy and TGA. See DOI: 10.1039/c6nr01129b

Crocoite: An unusual mode of occurence for lead in coal

USGS Publications Warehouse

Li, Z.; Moore, T.A.; Weaver, S.D.; Finkelman, R.B.

2001-01-01

What is believed to be a very unusual mode of occurrence for lead in coal has been identified as crocoite (PbCrO4). As part of a larger study on trace elements and mineralogy in the Cretaceous Main Seam in New Zealand, crocoite was found in raw coal samples within the lower part of the coal seam. X-ray diffraction (XRD) and bulk chemical data from a SEM equipped with an energy dispersive X-ray analyser (EDXA) have confirmed the identity of this mineral. This is apparently the first time that crocoite has been reported in coal. Crocoite usually occurs only in the oxidised zone of lead mineral deposits. The occurrence of this mineral in the Main Seam coal implies that the deposit was exposed to an oxidising environment at some stage, most likely after coalification. Published by Elsevier Science B.V.

Changes in water absorptivity of slag based cement mortars exposed to sulphur-oxidising A. thiooxidans bacteria

NASA Astrophysics Data System (ADS)

Estokova, A.; Smolakova, M.; Luptakova, A.; Strigac, J.

2017-10-01

Water absorptivity is heavily influenced by the volume and connectivity of pores in the pore network of cement composites and has been used as an important parameter for quantifying their durability. To improve the durability and permeability of mortars, various mineral admixtures such as furnace slag, silica fume or fly ash are added into the mortar and concrete mixtures. These admixtures provide numerous important advantages such as corrosion control, improvement of mechanical and physical properties and better workability. This study investigated the changes in absorptivity of cement mortars with different amounts of mineral admixture, represented by granulated blast furnace slag, under aggressive bacterial influence. The water absorptivity of mortars specimens exposed to sulphur-oxidising bacteria A. thiooxidans for the period of 3 and 6 months has changed due to bio-corrosion-based degradation process. The differences in water absorptivity in dependence on the mortars composition have been observed.

Molecular artificial photosynthesis.

PubMed

Berardi, Serena; Drouet, Samuel; Francàs, Laia; Gimbert-Suriñach, Carolina; Guttentag, Miguel; Richmond, Craig; Stoll, Thibaut; Llobet, Antoni

2014-11-21

The replacement of fossil fuels by a clean and renewable energy source is one of the most urgent and challenging issues our society is facing today, which is why intense research has been devoted to this topic recently. Nature has been using sunlight as the primary energy input to oxidise water and generate carbohydrates (solar fuel) for over a billion years. Inspired, but not constrained, by nature, artificial systems can be designed to capture light and oxidise water and reduce protons or other organic compounds to generate useful chemical fuels. This tutorial review covers the primary topics that need to be understood and mastered in order to come up with practical solutions for the generation of solar fuels. These topics are: the fundamentals of light capturing and conversion, water oxidation catalysis, proton and CO2 reduction catalysis and the combination of all of these for the construction of complete cells for the generation of solar fuels.

Revealing the fate of the phenylcoumaran linkage during lignin oxidation reactions.

PubMed

Lahive, Ciaran W; Lancefield, Christopher S; Codina, Anna; Kamer, Paul C J; Westwood, Nicholas J

2018-03-14

The fate of most lignin linkages, other than the β-O-4, under selective oxidation conditions is largely unknown. In this work we use advanced β-5 lignin model compounds to identify the fate of phenylcoumaran units in a softwood lignin during oxidation with DDQ. By using model compounds combined with detailed characterisation of the oxidised lignin polymer using HSQC and HMBC NMR we show that phenylcoumarones are a major product, and therefore constitute a novel non-native β-5 linkage in oxidised lignins. Additionally, the reactivity of these units in lignin led us to further investigate their connectivity in lignin, showing that they are found as both phenolic and etherified units. The findings and approach developed here will help improve the efficiency of selective oxidative lignin depolymerisation processes, particularly those aimed at the upgrading of softwood lignin in which phenylcoumarans are a major linkage.

Optimisation of the Photonic Efficiency of TiO2 Decorated on MWCNTs for Methylene Blue Photodegradation.

PubMed

Abdullahi, Nura; Saion, Elias; Shaari, Abdul Halim; Al-Hada, Naif Mohammed; Keiteb, Aysar

2015-01-01

MWCNTs/TiO2 nanocomposite was prepared by oxidising MWCNT in H2SO4/HNO3 then decorating it with TiO2-p25 nanopowder. The composites were characterised using XRD, TEM, FT-IR PL and UV-vis spectroscopy. The TEM images have shown TiO2 nanoparticles immobilised onto the sidewalls of the MWCNTs. The UV-vis spectrum confirms that the nanocomposites can significantly absorb more light in the visible regions compared with the commercial TiO2 (P25). The catalytic activity of these nanocomposites was determined by photooxidation of MB aqueous solution in the presence of visible light. The MWCNTs/TiO2 (1:3) mass ratio showed maximum degradation efficiency. However, its activity was more favourable in alkaline and a neutral pH than an acidic medium.

Consequences of CO2-rich water intrusion into the Critical Zone

NASA Astrophysics Data System (ADS)

Gal, Frédérick; Lions, Julie

2017-04-01

From a geochemical point of view, the sensitivity of the Critical Zone to hazards is not only linked to its proximity to the surface. It may also be linked to - albeit less common - intrusion of upward migrating fluids. One of the hazard scenarios to observe these pathways in surface environments is the occurrence of CO2-rich fluid leakage from deeper horizons and especially leakage from reservoir in the case of underground storage such as Carbon Storage applications. Much effort is done to prevent this risk but it necessary to consider the mitigation of this leak to insure safe storage. Numerous active or planned CO2 storage sites belong to large sedimentary basins. In that perspective, a CO2 injection has been performed in a multi-layered - carbonated aquifer (Beauce aquifer) from the Paris basin as this basin has been considered for such applications. The aquifer mineralogy of the targeted site is dominated by calcite (95 to 98%) with traces of quartz and clay minerals. Around 10,000 liters of CO2 were injected at 50 m depth during a series of gaseous pulsed injections for 5 days. After 3 days of incubation in the aquifer, the groundwater was pumped during 5 days allowing the recovery of 140 m3 of backward water. Physico-chemical parameters, major and trace elements concentrations and dissolved CO2 concentrations were monitored to evaluate water-rock interactions occurring within the aquifer and impacts onto water quality. Main changes that were observed during the CO2 release are in good agreement with results from previous experiments performed worldwide. A strong decrease of the pH value (2 units), a rise of the electrical conductivity (2 fold) and changes in the redox conditions (from oxidising to less oxidising) are monitored few hours after the initiation of the pumping. The dissolution of CO2 induces a drop of pH that favours water-rock interaction processes. The kinetic of reactions appears to be dominated by the dissolution of carbonate, mainly calcite, and probably by desorption processes onto clay minerals. Thus higher concentrations in HCO3 (+225%), Ca (+95%), Mg (+45%), Na (+14%) and SiO2 (+11%) as major elements and in Sr, Mn, Ba, B, As or Li as trace elements (2 to 3 fold increase) were monitored. Congruent rise in the concentration in dissolved CO2 is also observed. Nonetheless, the effects onto water physico-chemical parameters and water chemistry are transient and vanished in few days (4-5) when pumping is done. In the case of a punctual leakage event, even if pumping was not performed, natural flow of the water will also have induced natural attenuation and progressive vanish of anomalies. From a site management perspective, this suggests that sudden and time limited events may not be noticeable in the near surface if the monitoring locations are located remotely from the source. This highlights the need to have extensive site characterization prior setting a storage site.

Kinetics of NH3 -oxidation, NO-turnover, N2 O-production and electron flow during oxygen depletion in model bacterial and archaeal ammonia oxidisers.

PubMed

Hink, Linda; Lycus, Pawel; Gubry-Rangin, Cécile; Frostegård, Åsa; Nicol, Graeme W; Prosser, James I; Bakken, Lars R

2017-12-01

Ammonia oxidising bacteria (AOB) are thought to emit more nitrous oxide (N 2 O) than ammonia oxidising archaea (AOA), due to their higher N 2 O yield under oxic conditions and denitrification in response to oxygen (O 2 ) limitation. We determined the kinetics of growth and turnover of nitric oxide (NO) and N 2 O at low cell densities of Nitrosomonas europaea (AOB) and Nitrosopumilus maritimus (AOA) during gradual depletion of TAN (NH 3  + NH4+) and O 2 . Half-saturation constants for O 2 and TAN were similar to those determined by others, except for the half-saturation constant for ammonium in N. maritimus (0.2 mM), which is orders of magnitudes higher than previously reported. For both strains, cell-specific rates of NO turnover and N 2 O production reached maxima near O 2 half-saturation constant concentration (2-10 μM O 2 ) and decreased to zero in response to complete O 2 -depletion. Modelling of the electron flow in N. europaea demonstrated low electron flow to denitrification (≤1.2% of the total electron flow), even at sub-micromolar O 2 concentrations. The results corroborate current understanding of the role of NO in the metabolism of AOA and suggest that denitrification is inconsequential for the energy metabolism of AOB, but possibly important as a route for dissipation of electrons at high ammonium concentration. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.

Reactions of sterols with pyridinium chlorochromate.

PubMed

Ifzal, S M; Ahmed, R; Haque, I U

1988-01-01

Reaction of pyridinium chlorochromate with cyclohexanol and several C(3)-sterols have been investigated. It has been found that the equatorieal C(3)-sterols axe easily oxidised in good yield to give corresponding ketosteioids while the axial sterols give poor yields.

Aldose reductase inhibitory, anti-cataract and antioxidant potential of selected medicinal plants from the Marathwada region, India.

PubMed

Gacche, R N; Dhole, N A

2011-04-01

The water, ethanol and chloroform extracts of selected plants such as Adhatoda vasica (L.) (Acanthaceae), Caesalpinia bonduc (L.), Cassia fistula (L.) (Caesalpiniaceae) and Biophytum sensitivum (L.) (Oxalidaceae) were evaluated for rat lens aldose reductase inhibitory (RLAR) potential, anti-cataract and antioxidant activities. All the samples inhibited the aldose reductase considerably and exhibited anti-cataract activity, while C. fistula (IC(50), 0.154 mg mL(-1)) showed significant RLAR inhibitory activity as compared to the other tested samples, and was further found to be more effective in maintaining sugar-induced lens opacity in the rat lens model. The antioxidant potential of plant extracts was determined using DPPH (2,2-diphenyl-1-picryl hydrazine), hydroxyl (OH), nitric oxide (NO) and hydrogen peroxide (H(2)O(2)) scavenging activities, along with determination of reducing power, ferrous ion chelating ability and inhibition of polyphenol oxidase (PPO). The extracts of the tested plant showed significant free radical scavenging activities and inhibited the activity of enzyme PPO, a model oxidising enzyme. The plant samples were found to possess considerable amounts of vitamin C, total polyphenols and flavonoids.

Impact of Ocean Acidification on Fluxes of non-CO2 Climate-Active Species: Report from the GESAMP WG38 workshop

NASA Astrophysics Data System (ADS)

Suntharalingam, Parvadha; Gehlen, Marion; Hopkins, Frances; Duce, Robert; Jickells, Tim; Gesamp WG38 Workshop, Participants

2017-04-01

Most investigations of the impact of ocean acidification (OA) have focused on changes in oceanic uptake of anthropogenic CO2, the resulting shifts in carbonate chemical equilibria, and the consequences for marine calcifying organisms. Little attention has been paid to the direct impacts of OA on the ocean sources of a range of other gaseous and aerosol species that are influential in regulating radiative forcing, atmospheric oxidising capacity and atmospheric chemistry. The oceanic processes governing emissions of these species are frequently sensitive to the changes in pH and ocean pCO2 accompanying ocean acidification. Such processes include, for example, metabolic rates of microbial activity, levels of surface primary production, ecosystem composition, and photo-chemical and microbially mediated production/loss pathways for individual species. The direct and indirect influences of these factors on oceanic fluxes of non-CO2 trace-gases and aerosols, and the subsequent feedbacks to climate remain highly uncertain. To address these issues UN/GESAMP Working Group 38, The Atmospheric Input of Chemicals to the Ocean, convened a workshop on this topic at the University of East Anglia in February, 2017. The goals of this workshop are to review and synthesize the current science on the direct impacts of ocean acidification on marine emissions to the atmosphere of key species important for climate, and atmospheric chemistry; and to identify the primary needs for new research to improve process understanding and to quantify the impact of ocean acidification on these marine fluxes (i.e., provide recommendations on the specific laboratory process studies, field measurements and model analyses needed to support targeted research activities on this topic). The results, conclusions, and recommendations of this workshop will be presented.

The non-participation of organic sulphur in acid mine drainage generation

USGS Publications Warehouse

Casagrande, D.J.; Finkelman, R.B.; Caruccio, F.T.

1989-01-01

Acid mine drainage is commonly associated with land disturbances that encounter and expose iron sulphides to oxidising atmospheric conditions. The attendant acidic conditions solubilise a host of trace metals. Within this flow regime the potential exists to contaminate surface drinking water supplies with a variety of trace materials. Accordingly, in evaluating the applications for mines located in the headwaters of water sheds, the pre-mining prediction of the occurrence of acid mine drainage is of paramount importance. There is general agreement among investigators that coal organic sulphur is a nonparticipant in acid mine drainage generation; however, there is no scientific documentation to support this concensus. Using simulated weathering, kinetic, mass balance, petrographic analysis and a peroxide oxidation procedure, coal organic sulphur is shown to be a nonparticipant in acid mine drainage generation. Calculations for assessing the acid-generating potential of a sedimentary rock should not include organic sulphur content. ?? 1989 Sciences and Technology Letters.

The oxidation of Inconel-690 alloy at 600 K in air

NASA Astrophysics Data System (ADS)

Allen, G. C.; Dyke, J. M.; Harris, S. J.; Morris, A.

1988-03-01

The alloy Inconel-690 has been oxidised at 600 K in air for periods varying between 30 s and 120 h and the composition of the oxide layer formed examined by scanning Auger microscopy (SAM), scanning electron microscopy with energy dispersive analysis of X-rays (SEM/EDAX), secondary ion mass spectrometry (SIMS) and X-ray photoelectron spectroscopy (XPS). Analysis of the spectra revealed the formation of a layer of essentially α-Cr 2O 3 at room temperature. Oxidation at 600 K resulted in the formation of a duplex oxide film with a thin outer layer of iron(III) oxide. Beneath this was a mixed chromium, iron, nickel oxide. Following 8 h of oxidation at 600 K the oxide was approximately 10 nm thick but this was found to vary with the physical surface of the underlying alloy which also appeared to affect the relative rates of diffusion of the ionic species during film growth.

Surface polymerization of (3,4-ethylenedioxythiophene) probed by in situ scanning tunneling microscopy on Au(111) in ionic liquids.

PubMed

Ahmad, Shahzada; Carstens, Timo; Berger, Rüdiger; Butt, Hans-Jürgen; Endres, Frank

2011-01-01

The electropolymerization of 3,4-ethylenedioxythiophene (EDOT) to poly(3,4-ethylenedioxythiophene) (PEDOT) was investigated in the air and water-stable ionic liquids 1-hexyl-3-methylimidazolium tris(pentafluoroethyl) trifluorophosphate [HMIm]FAP and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) amide [EMIm]TFSA. In situ scanning tunnelling microscopy (STM) results show that the electropolymerization of EDOT in the ionic liquid can be probed on the nanoscale. In contrast to present understanding, it was observed that the EDOT can be oxidised in ionic liquids well below its oxidation potential and the under potential growth of polymer was visualized by in situ STM. These results serve as the first study to confirm the under potential growth of conducting polymers in ionic liquids. Furthermore, ex situ microscopy measurements were performed. Quite a high current of 670 nA was observed on the nanoscale by conductive scanning force microscopy (CSFM).

Effects of sonication on co-precipitation synthesis and activity of copper manganese oxide catalyst to remove methane and sulphur dioxide gases.

PubMed

Yap, Yeow Hong; Lim, Mitchell S W; Lee, Zheng Yee; Lai, Kar Chiew; Jamaal, Muhamad Ashraf; Wong, Farng Hui; Ng, Hoon Kiat; Lim, Siew Shee; Tiong, T Joyce

2018-01-01

The utilisation of ultrasound in chemical preparation has been the focus of intense study in various fields, including materials science and engineering. This paper presents a novel method of synthesising the copper-manganese oxide (Hopcalite) catalyst that is used for the removal of volatile organic compounds and greenhouse gases like carbon monoxide. Several samples prepared under different conditions, with and without ultrasound, were subjected to a series of characterisation tests such as XRD, BET, FE-SEM, EDX, TPR-H 2 , TGA and FT-IR in order to establish their chemical and physical properties. A series of catalytic tests using a micro-reactor were subsequently performed on the samples in order to substantiate the aforementioned properties by analysing their ability to oxidise compressed natural gas (CNG), containing methane and sulphur dioxide. Results showed that ultrasonic irradiation of the catalyst led to observable alterations in its morphology: surfaces of the particles were noticeably smoothed and an increased in amorphicity was detected. Furthermore, ultrasonic irradiation has shown to enhance the catalytic activity of Hopcalite, achieving a higher conversion of methane relative to non-sonicated samples. Varying the ultrasonic intensity also produced appreciable effects, whereby an increase in intensity results in a higher conversion rate. The catalyst sonicated at the highest intensity of 29.7W/cm 2 has a methane conversion rate of 13.5% at 400°C, which was the highest among all the samples tested. Copyright © 2017 Elsevier B.V. All rights reserved.

Silver deposition on polypyrrole films electrosynthesised onto Nitinol alloy. Corrosion protection and antibacterial activity.

PubMed

Saugo, M; Flamini, D O; Brugnoni, L I; Saidman, S B

2015-11-01

The electrosynthesis of polypyrrole films onto Nitinol from sodium salicylate solutions of different concentrations is reported. The morphology and corrosion protection properties of the resulting coatings were examined and they both depend on the sodium salicylate concentration. The immobilisation of silver species in PPy films constituted by hollow rectangular microtubes was studied as a function of the polymer oxidation degree. The highest amount of silver was deposited when the coated electrode was prepolarised at -1.00V (SCE) before silver deposition, suggesting an increase in the amount of non-oxidised segments in the polymer. Finally, the antibacterial activity of the coating against the Gram positive Staphylococcus aureus and Staphylococcus epidermidis bacteria was evaluated. Both strains resulted sensitive to the modified coatings, obtaining a slightly better result against S. aureus. Copyright © 2015 Elsevier B.V. All rights reserved.

Comparative investigation on the effect of T-2 mycotoxin on lipid peroxidation and antioxidant status in different poultry species.

PubMed

Mézes, M; Barta, M; Nagy, G

1999-02-01

The effect of low dose T-2 toxin was investigated in chicken, duck and goose. The purpose of the present study was to investigate the effect of T-2 toxin on the lipid peroxidation and on the activity of glutathione redox system (amount of reduced and oxidised glutathione and the activity of glutathione peroxidase) in blood and liver. The treatment lasted days and two samples were taken, first at the time of lowest feed intake and second when the intake was the same as the control. It was found, that lipid per oxidation as detected by the amount of malondialdehyde increased in all of the species and tissues but the changes varied by species. The most sensitive species was goose followed by duck and chicken, and the most sensitive tissue was the liver followed by blood plasma and red blood cells.

Lipoxygenase activity in different species of sweet lupin (Lupinus L.) seeds and flakes.

PubMed

Stephany, Michael; Bader-Mittermaier, Stephanie; Schweiggert-Weisz, Ute; Carle, Reinhold

2015-05-01

Lipoxygenase (LOX)-catalysed degradation of polyunsaturated fatty acids is supposed to be a major cause of undesirable off-flavour development in legumes. In the present study, a photometric LOX assay including adequate sample workup was adapted to lupin seeds, kernels and flakes, respectively. Optimum reaction conditions were at pH 7.5 using a phosphate buffer concentration of 150 mmol l(-1) without the addition of sodium chloride. The LOX activities of different lupin species and varieties were compared. Significant variations among the species and varieties ranging from 50 to 1004 units mg(-1) protein were determined, being significantly lower than soybean LOX activity. Hulling and flaking of the seeds resulted in a 15% increase of LOX activity. In contrast to soy and other legumes, LOX from lupin only converted free fatty acids, whereas trilinolein and β-carotene were not oxidised. Consequently, according to the established classification, lupin LOX activity may be assigned to the LOX type-1, which, to the best of our knowledge, was demonstrated for the first time. Copyright © 2014 Elsevier Ltd. All rights reserved.

Induction of glutathione synthesis and glutathione reductase activity by abiotic stresses in maize and wheat.

PubMed

Kocsy, Gábor; Szalai, Gabriella; Galiba, Gábor

2002-06-21

The effect of different abiotic stresses (extreme temperatures and osmotic stress) on the synthesis of glutathione and hydroxymethylglutathione, on the ratio of the reduced to oxidised forms of these thiols (GSH/GSSG, hmGSH/hmGSSG), and on the glutathione reductase (GR) activity was studied in maize and wheat genotypes having different sensitivity to low temperature stress. Cold treatment induced a greater increase in total glutathione (TG) content and in GR activity in tolerant genotypes of both species than in sensitive ones. The GSH/GSSG and hmGSH/hmGSSG ratios were increased by this treatment only in the frost-tolerant wheat variety. High-temperature stress increased the TG content and the GSH/GSSG ratio only in the chilling-sensitive maize genotype, but GR activity was greater after this treatment in both maize genotypes. Osmotic stress resulted in a great increase in the TG content in wheat and the GR activity in maize. The amount of total hydroxymethylglutathione increased following all stress treatments. These results indicate the involvement of these antioxidants in the stress responses of wheat and maize.

Control of oxidation-reduction potential during Cheddar cheese ripening and its effect on the production of volatile flavour compounds.

PubMed

Caldeo, Veronica; Hannon, John A; Hickey, Dara-Kate; Waldron, Dave; Wilkinson, Martin G; Beresford, Thomas P; McSweeney, Paul L H

2016-11-01

In cheese, a negative oxidation-reduction (redox) potential is required for the stability of aroma, especially that associated with volatile sulphur compounds. To control the redox potential during ripening, redox agents were added to the salted curd of Cheddar cheese before pressing. The control cheese contained only salt, while different oxidising or reducing agents were added with the NaCl to the experimental cheeses. KIO3 (at 0·05, 0·1 and 1%, w/w) was used as the oxidising agent while cysteine (at 2%, w/w) and Na2S2O4 (at 0·05 and 0·1%, w/w) were used as reducing agents. During ripening the redox potential of the cheeses made with the reducing agents did not differ significantly from the control cheese (E h ≈ -120 mV) while the cheeses made with 0·1 and 0·05% KIO3 had a significantly higher and positive redox potential in the first month of ripening. Cheese made with 1% KIO3 had positive values of redox potential throughout ripening but no starter lactic acid bacteria survived in this cheese; however, numbers of starter organisms in all other cheeses were similar. Principal component analysis (PCA) of the volatile compounds clearly separated the cheeses made with the reducing agents from cheeses made with the oxidising agents at 2 month of ripening. Cheeses with reducing agents were characterized by the presence of sulphur compounds whereas cheeses made with KIO3 were characterized mainly by aldehydes. At 6 month of ripening, separation by PCA was less evident. These findings support the hypothesis that redox potential could be controlled during ripening and that this parameter has an influence on the development of cheese flavour.

Meteorite-associated growth physiology of the iron oxidising extremophile Metallosphaera sedula

NASA Astrophysics Data System (ADS)

Zebec, Ziga; Rittmann, Simon; Schleper, Christa; Milojevic, Tetyana

2015-04-01

Extremophiles cherry pick the habitats at the edge of living limits, shaping the life under inhospitable conditions. Such microbes are characterised by functional capabilities required for survival in harsh and extreme environments. These living entities serve as models for a life on early Earth with its severe and ancient habitats, providing an understanding of the extent of biology on Earth, and enabling a discovery of its wider presence in the universe. The Fe-oxidising archaeon Metallosphaera sedula inhabits extreme environments, flourishing in hot acid and exhibiting unusual heavy-metal resistance. This chemolithotrophic archaea thrives at 73°C and pH 2, utilizing energy derived from metal oxidation. Iron and sulphur compounds are preferentially required for its growth. Owing its physiological versatility, M. sedula is able to grow efficiently chemoauto- and chemomixotrophically using pyrite, chalcopyrite or sulfur compounds as an energy source and can also grow heterotrophically using yeast extract representing an excellent model organism for basic research into bioleaching processes. Stimulated by its exceptional physiological properties, we have set out to assess the survival potential of M. sedula by investigating the viability of this archaeon living on and interacting with minerals of non-terrestrial origin. Initial results demonstrate that the iron oxidising thermoacidophile M. sedula utilizes metals trapped within stony meteorites as the most preferential energy source, resulting in i) one order of magnitude higher growth rate comparatively to the other energy substrates of terrestrial origin (sulfide ores, hydrogen, iron sulfate) ii) a drastic shift in a lower temperature limit for this microbe. A comprehensive complex of genetic, biochemical and geochemical techniques will be applied to analyze microbial-meteorite liaison.

Influence of G-jitter on the characteristics of a non-premixed flame: Experimental approach

NASA Astrophysics Data System (ADS)

Joulain, Pierre; Cordeiro, Pierre; Rouvreau, Sébastien; Legros, Guillaume; Fuentes, Andres; Torero, José L.

2005-03-01

The combustion of a flat plate in a boundary layer under microgravity conditions, which was first described by Emmons, is studied using a gas burner. Magnitude of injection and blowing velocities are chosen to be characteristic of pyrolyzing velocity of solid fuels, and of ventilation systems in space stations. These velocities are about 0.1 m/s for oxidiser flow and 0.004m/s for fuel flow. In this configuration, flame layout results from a coupled interaction between oxidiser flow, fuel flow and thermal expansion. Influences of these parameters are studied experimentally by means of flame length and standoff distance measurements using CH* chemiluminescence's and visible emission of the flame. Flow was also studied with Particle Image Velocimetry (PIV). Inert flows, with and without injection, and reacting flow in a microgravity environment were considered to distinguish aerodynamic from thermal effect. Thermal expansion effects have been shown by means of the acceleration of oxidiser flow. Three-dimensional effects, which are strongly marked for high injection velocities were studied. Three-dimensional tools adaptability to parabolic flights particular conditions were of concern. Flame sensitivity to g-jitters was investigated according to g-jitters frequency and range involved by parabolic flights. It appears that flame location (standoff distance), flame characteristics (length, thickness, brightness) and the aerodynamic field of the low velocity reacting flow are very much affected by the fluctuation of the gravity level or g-jitter. The lower the g-jitter frequency is, the higher the perturbation. Consequently it is difficult to perform relevant experiments for a main flow velocity lower than 0.05m/s. DNS calculations confirm the present observations, but most of the results are presented elsewhere.

Fatty acid metabolism (desaturation, elongation and beta-oxidation) in rainbow trout fed fish oil- or linseed oil-based diets.

PubMed

Turchini, Giovanni M; Francis, David S

2009-07-01

In consideration of economical and environmental concerns, fish oil (FO) substitution in aquaculture is the focus of many fish nutritionists. The most stringent drawback of FO replacement in aquafeeds is the consequential modification to the final fatty acid (FA) make-up of the fish fillet. However, it is envisaged that a solution may be achieved through a better understanding of fish FA metabolism. Therefore, the present study investigated the fate of individual dietary FA in rainbow trout (Oncorhynchus mykiss) fed a FO-based diet (rich in 20 : 5n-3) or a linseed oil-based diet (LO; rich in 18 : 3n-3). The study demonstrated that much of the 18 : 3n-3 content from the LO diet was oxidised and, despite the significantly increased accretion of Delta-6 and Delta-5 desaturated FA, a 2- and 3-fold reduction in the fish body content of 20 : 5n-3 and 22 : 6n-3, respectively, compared with the FO-fed fish, was recorded. The accretion of longer-chain FA was unaffected by the dietary treatments, while there was a greater net disappearance of FA provided in dietary surplus. SFA and MUFA recorded a net accretion of FA produced ex novo. In the fish fed the FO diet, the majority of dietary 20 : 5n-3 was accumulated (53.8 %), some was oxidised (14.7 %) and a large proportion (31.6 %) was elongated and desaturated up to 22 : 6n-3. In the fish fed the LO diet, the majority of dietary 18 : 3n-3 was accumulated (58.1 %), a large proportion was oxidised (29.5 %) and a limited amount (12.4 %) was bio-converted to longer and more unsaturated homologues.

Combustion characteristics of Malaysian oil palm biomass, sub-bituminous coal and their respective blends via thermogravimetric analysis (TGA).

PubMed

Idris, Siti Shawalliah; Rahman, Norazah Abd; Ismail, Khudzir

2012-11-01

The combustion characteristics of Malaysia oil palm biomass (palm kernel shell (PKS), palm mesocarp fibre (PMF) and empty fruit bunches (EFB)), sub-bituminous coal (Mukah Balingian) and coal/biomass blends via thermogravimetric analysis (TGA) were investigated. Six weight ratios of coal/biomass blends were prepared and oxidised under dynamic conditions from temperature 25 to 1100°C at four heating rates. The thermogravimetric analysis demonstrated that the EFB and PKS evolved additional peak besides drying, devolatilisation and char oxidation steps during combustion. Ignition and burn out temperatures of blends were improved in comparison to coal. No interactions were observed between the coal and biomass during combustion. The apparent activation energy during this process was evaluated using iso-conversional model free kinetics which resulted in highest activation energy during combustion of PKS followed by PMF, EFB and MB coal. Blending oil palm biomass with coal reduces the apparent activation energy value. Copyright © 2012 Elsevier Ltd. All rights reserved.

Mineralogy and geochemistry of efflorescent minerals on mine tailings and their potential impact on water chemistry.

PubMed

Grover, B P C; Johnson, R H; Billing, D G; Weiersbye, I M G; Tutu, H

2016-04-01

In the gold mining Witwatersrand Basin of South Africa, efflorescent mineral crusts are a common occurrence on and nearby tailings dumps during the dry season. The crusts are readily soluble and generate acidic, metal- and sulphate-rich solutions on dissolution. In this study, the metal content of efflorescent crusts at an abandoned gold mine tailings dump was used to characterise surface and groundwater discharges from the site. Geochemical modelling of the pH of the solution resulting from the dissolution of the crusts was used to better understand the crusts' potential impact on water chemistry. The study involved two approaches: (i) conducting leaching experiments on oxidised and unoxidised tailings using artificial rainwater and dilute sulphuric acid and correlating the composition of crusts to these leachates and (ii) modelling the dissolution of the crusts in order to gain insight into their mineralogy and their potential impact on receiving waters. The findings suggested that there were two chemically distinct discharges from the site, namely an aluminium- and magnesium-rich surface water plume and an iron-rich groundwater plume. The first plume was observed to originate from the oxidised tailings following leaching with rainwater while the second plume originated from the underlying unoxidised tailings with leaching by sulphuric acid. Both groups of minerals forming from the respective plumes were found to significantly lower the pH of the receiving water with simulations of their dissolution found to be within 0.2 pH units of experimental values. It was observed that metals in a low abundance within the crust (for example, iron) had a stronger influence on the pH of the resulting solutions than metals in a greater abundance (aluminium or magnesium). Techniques such as powder X-ray diffraction (PXRD) and in situ mineral determination techniques such as remote sensing can effectively determine the dominant mineralogy. However, the minerals or metals incorporated through solid solution into bulk mineralogy that dominates the chemistry of the solutions upon their dissolution may occur in minor quantities that can only be predicted using chemical analysis. Their mineralogy can be predicted using geochemical modelling and can provide a set of hypothetical minerals that upon dissolution yield a solution similar to that of the actual crusts. This realisation has a bearing on decision-making such as in risk assessment and designing pollutant mitigation strategies.

Methane-Carbon Flow into the Benthic Food Web at Cold Seeps – A Case Study from the Costa Rica Subduction Zone

PubMed Central

Niemann, Helge; Linke, Peter; Knittel, Katrin; MacPherson, Enrique; Boetius, Antje; Brückmann, Warner; Larvik, Gaute; Wallmann, Klaus; Schacht, Ulrike; Omoregie, Enoma; Hilton, David; Brown, Kevin; Rehder, Gregor

2013-01-01

Cold seep ecosystems can support enormous biomasses of free-living and symbiotic chemoautotrophic organisms that get their energy from the oxidation of methane or sulfide. Most of this biomass derives from animals that are associated with bacterial symbionts, which are able to metabolize the chemical resources provided by the seeping fluids. Often these systems also harbor dense accumulations of non-symbiotic megafauna, which can be relevant in exporting chemosynthetically fixed carbon from seeps to the surrounding deep sea. Here we investigated the carbon sources of lithodid crabs (Paralomis sp.) feeding on thiotrophic bacterial mats at an active mud volcano at the Costa Rica subduction zone. To evaluate the dietary carbon source of the crabs, we compared the microbial community in stomach contents with surface sediments covered by microbial mats. The stomach content analyses revealed a dominance of epsilonproteobacterial 16S rRNA gene sequences related to the free-living and epibiotic sulfur oxidiser Sulfurovum sp. We also found Sulfurovum sp. as well as members of the genera Arcobacter and Sulfurimonas in mat-covered surface sediments where Epsilonproteobacteria were highly abundant constituting 10% of total cells. Furthermore, we detected substantial amounts of bacterial fatty acids such as i-C15∶0 and C17∶1ω6c with stable carbon isotope compositions as low as −53‰ in the stomach and muscle tissue. These results indicate that the white microbial mats at Mound 12 are comprised of Epsilonproteobacteria and that microbial mat-derived carbon provides an important contribution to the crab's nutrition. In addition, our lipid analyses also suggest that the crabs feed on other 13C-depleted organic matter sources, possibly symbiotic megafauna as well as on photosynthetic carbon sources such as sedimentary detritus. PMID:24116017

Methane-carbon flow into the benthic food web at cold seeps--a case study from the Costa Rica subduction zone.

PubMed

Niemann, Helge; Linke, Peter; Knittel, Katrin; MacPherson, Enrique; Boetius, Antje; Brückmann, Warner; Larvik, Gaute; Wallmann, Klaus; Schacht, Ulrike; Omoregie, Enoma; Hilton, David; Brown, Kevin; Rehder, Gregor

2013-01-01

Cold seep ecosystems can support enormous biomasses of free-living and symbiotic chemoautotrophic organisms that get their energy from the oxidation of methane or sulfide. Most of this biomass derives from animals that are associated with bacterial symbionts, which are able to metabolize the chemical resources provided by the seeping fluids. Often these systems also harbor dense accumulations of non-symbiotic megafauna, which can be relevant in exporting chemosynthetically fixed carbon from seeps to the surrounding deep sea. Here we investigated the carbon sources of lithodid crabs (Paralomis sp.) feeding on thiotrophic bacterial mats at an active mud volcano at the Costa Rica subduction zone. To evaluate the dietary carbon source of the crabs, we compared the microbial community in stomach contents with surface sediments covered by microbial mats. The stomach content analyses revealed a dominance of epsilonproteobacterial 16S rRNA gene sequences related to the free-living and epibiotic sulfur oxidiser Sulfurovum sp. We also found Sulfurovum sp. as well as members of the genera Arcobacter and Sulfurimonas in mat-covered surface sediments where Epsilonproteobacteria were highly abundant constituting 10% of total cells. Furthermore, we detected substantial amounts of bacterial fatty acids such as i-C15∶0 and C17∶1ω6c with stable carbon isotope compositions as low as -53‰ in the stomach and muscle tissue. These results indicate that the white microbial mats at Mound 12 are comprised of Epsilonproteobacteria and that microbial mat-derived carbon provides an important contribution to the crab's nutrition. In addition, our lipid analyses also suggest that the crabs feed on other (13)C-depleted organic matter sources, possibly symbiotic megafauna as well as on photosynthetic carbon sources such as sedimentary detritus.

Electrical degradation of triarylamine-based light-emitting polymer diodes monitored by micro-Raman spectroscopy

NASA Astrophysics Data System (ADS)

Kim, Ji-Seon; Ho, Peter K. H.; Murphy, Craig E.; Seeley, Alex J. A. B.; Grizzi, Ilaria; Burroughes, Jeremy H.; Friend, Richard H.

2004-03-01

Although much progress has been made in improving polymer light-emitting diode performance, there has been little work to address device intrinsic degradation mechanisms due to the challenge of tracking minute chemical reactions in the 100-nm-thick buried active layers during operation. Here we have elucidated a hole-mediated electrical degradation of triarylamine-based blue polymer diodes using in situ Raman microspectroscopy. A slow irreversible hole-doping of polymer adjacent to the hole-injecting conducting-polymer leads to formation of oxidised triarylamine species counterbalanced by anions from the conducting-polymer. These charged species act as luminescence quenchers and hinder further hole injection across the interface leading to significant decreases in current density at low voltages.

Lipase-Produced Hydroxytyrosyl Eicosapentaenoate is an Excellent Antioxidant for the Stabilization of Omega-3 Bulk Oils, Emulsions and Microcapsules.

PubMed

Akanbi, Taiwo Olusesan; Barrow, Colin James

2018-01-29

In this study, several lipophilic hydroxytyrosyl esters were prepared enzymatically using immobilized lipase from Candida antarctica B. Oxidation tests showed that these conjugates are excellent antioxidants in lipid-based matrices, with hydroxytyrosyl eicosapentaenoate showing the highest antioxidant activity. Hydroxytyrosyl eicosapentaenoate effectively stabilized bulk fish oil, fish-oil-in-water emulsions and microencapsulated fish oil. The stabilizing effect of this antioxidant may either be because it orients itself with the omega-3 fatty acids in the oil, thereby protecting them against oxidation, or because this unstable fatty acid can preferentially oxidise, thus providing an additional mechanism of antioxidant protection. Hydroxytyrosyl eicosapentaenoate itself was stable for one year when stored at -20 °C.

[The expressions of anxiety in the elderly. Their diagnosis and therapy].

PubMed

Scapicchio, P L

1995-10-01

Among the most common manifestations of anxiety in the elderly are those associated with neurological disorders. The etiology is often unclear, as anxiety and agitation may be a consequence of insight into the cognitive impairment rather than the direct expression of the neurological deficit. Benzodiazepines are the treatment of choice, particularly the 3-OH compounds that are non oxidised and without active metabolites. Concern about the use of benzodiazepines in the elderly may have been overstated. If used judiciously this class of drugs can prove extremely helpful in reducing day-time anxiety and night-time insomnia. Other medications that are commonly used to treat agitation and disruptive behaviour in demented elderly patients include antipsychotics, beta-blockers, trazodone, buspirone, anticonvulsants.

Gold and palladium minerals (including empirical PdCuBiSe3) from the former Roter Bär mine, St. Andreasberg, Harz Mountains, Germany: a result of low-temperature, oxidising fluid overprint

NASA Astrophysics Data System (ADS)

Cabral, Alexandre Raphael; Ließmann, Wilfried; Lehmann, Bernd

2015-10-01

At Roter Bär, a former underground mine in the polymetallic deposits of St. Andreasberg in the middle-Harz vein district, Germany, native gold and palladium minerals occur very locally in clausthalite-hematite pockets of few millimetres across in carbonate veinlets. The native gold is a Au-Ag intermetallic compound and the palladium minerals are characterised as mertieite-II [Pd8(Sb,As)3] and empirical PdCuBiSe3 with some S. The latter coexists with bohdanowiczite (AgBiSe2), a mineral that is stable below 120 °C. The geological setting of Roter Bär, underneath a post-Variscan unconformity, and its hematite-selenide-gold association suggest that oxidising hydrothermal brines of low temperature were instrumental to the Au-Pd mineralisation. The Roter Bär Au-Pd mineralisation can be explained by Permo-Triassic, red-bed-derived brines in the context of post-Variscan, unconformity-related fluid overprint.

Effects of CO2 plant extracts on triacylglycerol oxidation in Atlantic salmon during cooking and storage.

PubMed

Tarvainen, Marko; Nuora, Anu; Quirin, Karl-Werner; Kallio, Heikki; Yang, Baoru

2015-04-15

Increasing concern of consumers on the safety of synthetic food additives has created high interest in natural preservatives in food industry. Plant extracts produced by supercritical CO2 technology from rosemary (R), oregano (O) and an antimicrobial blend (AB) consisting of seven different plants were studied for their effects on lipid oxidation in Atlantic salmon (Salmo salar). Fish pieces were marinated with rapeseed oil containing 0, 1, 2 or 4 g of plant extracts/kg of fish. After cooking the pieces were stored in refrigerator for 26 days. Peroxide values (PVs) were determined and oxidised triacylglycerols (TAGs) measured by UHPLC-ESI/MS at 0, 7, 14 and 26 days of storage. During the first two weeks of storage, AB delayed oxidation by at least one week compared to control samples as shown by PVs (<10 meq. O2) and by the oxidised TAGs. Oregano and rosemary showed also some antioxidative potential. Copyright © 2014 Elsevier Ltd. All rights reserved.

Passive landfill gas emission - Influence of atmospheric pressure and implications for the operation of methane-oxidising biofilters.

PubMed

Gebert, Julia; Groengroeft, Alexander

2006-01-01

A passively vented landfill site in Northern Germany was monitored for gas emission dynamics through high resolution measurements of landfill gas pressure, flow rate and composition as well as atmospheric pressure and temperature. Landfill gas emission could be directly related to atmospheric pressure changes on all scales as induced by the autooscillation of air, diurnal variations and the passage of pressure highs and lows. Gas flux reversed every 20 h on average, with 50% of emission phases lasting only 10h or less. During gas emission phases, methane loads fed to a connected methane oxidising biofiltration unit varied between near zero and 247 g CH4 h(-1)m(-3) filter material. Emission dynamics not only influenced the amount of methane fed to the biofilter but also the establishment of gas composition profiles within the biofilter, thus being of high relevance for biofilter operation. The duration of the gas emission phase emerged as most significant variable for the distribution of landfill gas components within the biofilter.

Chemiluminescence reactions with cationic, neutral, and anionic ruthenium(II) complexes containing 2,2'-bipyridine and bathophenanthroline disulfonate ligands.

PubMed

Francis, Paul S; Papettas, Dimitra; Zammit, Elizabeth M; Barnett, Neil W

2010-07-15

Ruthenium complexes containing 4,7-diphenyl-1,10-phenanthroline disulfonate (bathophenanthroline disulfonate; BPS) ligands, Ru(BPS)(3)(4-), Ru(BPS)(2)(bipy)(2-) and Ru(BPS)(bipy)(2), were compared to tris(2,2'-bipyridine)ruthenium(II) (Ru(bipy)(3)(2+)), including examination of the wavelengths of maximum absorption and corrected emission intensity, photoluminescence quantum yield, stability of their oxidised ruthenium(III) form, and relative chemiluminescence intensities and signal-to-blank ratios with cerium(IV) sulfate and six analytes (codeine, morphine cocaine, potassium oxalate, furosemide and hydrochlorothiazide) in acidic aqueous solution. The presence of BPS ligands in the complex increased the photoluminescence quantum yield, but decreased the stability of the oxidised form of the reagent. In contrast to previous evidence showing much greater electrochemiluminescence intensities using Ru(BPS)(2)(bipy)(2-) and Ru(BPS)(bipy)(2), these complexes did not provide superior chemiluminescence signals than their homoleptic analogues. Copyright 2010 Elsevier B.V. All rights reserved.

AL(0) in municipal waste incinerator ash

NASA Astrophysics Data System (ADS)

Stipp, S. L.; Ronsbo, J. G.; Zunic, T. B.; Christensen, T. H.

2003-04-01

Disposal of municipal waste is a challenge to society. Waste volume is substantially decreased by incineration but residual ash usually contains a number of toxic components which must be immobilised to insure environmental protection. One element, chromium, is mobile and toxic in its oxidised state as Cr(VI) but it can be reduced to Cr(III) and immobilised. Reduction can be promoted by ash treatment with Fe(0) or Fe(II), but recent evidence shows that at least some Cr(VI) is reduced spontaneously in the ash. Aspects of ash behaviour suggest metallic aluminium as the reducing agent, but no direct evidence of Al(0) has been found until now. We examined filter ash from an energy-producing, municipal-waste incinerator (Vest-forbrænding) near Copenhagen. X-ray diffraction (XRD) identified expected salts of Na, K and Ca such as halite, sylvite, calcite, anhydrite and gypsum as well as quartz, feldspar and some hematite. Wave-dispersive electron microprobe produced elemen-tal maps of the ash; Al-rich areas were analysed quantitatively by comparison with standards. We identified metallic Al particles, averaging 50 to 100 micrometers in di-ameter, often with a fractured, glassy border of aluminum oxide. The particles were porous, explaining fast Cr(VI) reduction and they contained thin exsolution lamellae of Al-alloys of Pb and Cu or Mn, Fe and Ag, which provide clues of the Al(0) origin in the waste. Sometimes Al(0) occurred inside glassy globes of Al2O3. Time-of-flight secondary ion mass spectroscopy (TOF-SIMS) and X-ray photoelectron spectroscopy (XPS) proved that surface Al concentrations on ash particles were below detection, confirming reactivity of the Al(0) bulk. The persistence of reduced Al through the highly oxidising combustion procedure comes as a surprise and is a benefit in the immobilisation of Cr(VI) from municipal-waste incineration residues.

Surface polymerization of (3,4-ethylenedioxythiophene) probed by in situ scanning tunneling microscopy on Au(111) in ionic liquids

NASA Astrophysics Data System (ADS)

Ahmad, Shahzada; Carstens, Timo; Berger, Rüdiger; Butt, Hans-Jürgen; Endres, Frank

2011-01-01

The electropolymerization of 3,4-ethylenedioxythiophene (EDOT) to poly(3,4-ethylenedioxythiophene) (PEDOT) was investigated in the air and water-stable ionic liquids 1-hexyl-3-methylimidazolium tris(pentafluoroethyl) trifluorophosphate [HMIm]FAP and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) amide [EMIm]TFSA. In situscanning tunnelling microscopy (STM) results show that the electropolymerization of EDOT in the ionic liquid can be probed on the nanoscale. In contrast to present understanding, it was observed that the EDOT can be oxidised in ionic liquids well below its oxidation potential and the under potential growth of polymer was visualized by in situSTM. These results serve as the first study to confirm the under potential growth of conducting polymers in ionic liquids. Furthermore, ex situmicroscopy measurements were performed. Quite a high current of 670 nA was observed on the nanoscale by conductive scanning force microscopy (CSFM).The electropolymerization of 3,4-ethylenedioxythiophene (EDOT) to poly(3,4-ethylenedioxythiophene) (PEDOT) was investigated in the air and water-stable ionic liquids 1-hexyl-3-methylimidazolium tris(pentafluoroethyl) trifluorophosphate [HMIm]FAP and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) amide [EMIm]TFSA. In situscanning tunnelling microscopy (STM) results show that the electropolymerization of EDOT in the ionic liquid can be probed on the nanoscale. In contrast to present understanding, it was observed that the EDOT can be oxidised in ionic liquids well below its oxidation potential and the under potential growth of polymer was visualized by in situSTM. These results serve as the first study to confirm the under potential growth of conducting polymers in ionic liquids. Furthermore, ex situmicroscopy measurements were performed. Quite a high current of 670 nA was observed on the nanoscale by conductive scanning force microscopy (CSFM). Electronic supplementary information (ESI) available: In situ image of PEDOT in [HMIm]FAP and in situ studies of PEDOT grown in [EMIm]TFSA and redox behavior of PEDOT. See DOI: 10.1039/c0nr00579g

Methods for the detection of antioxidants which prevent age related diseases: a critical review with particular emphasis on human intervention studies.

PubMed

Hoelzl, C; Bichler, J; Ferk, F; Simic, T; Nersesyan, A; Elbling, L; Ehrlich, V; Chakraborty, A; Knasmüller, S

2005-03-01

It is well documented that reactive oxygen species (ROS) are involved in the aetiology of age related diseases. Over the last decades, strong efforts have been made to identify antioxidants in human foods and numerous promising compounds have been detected which are used for the production of supplements and functional foods. The present paper describes the advantages and limitations of methods which are currently used for the identification of antioxidants. Numerous in vitro methods are available which are easy to perform and largely used in screening trials. However, the results of such tests are only partly relevant for humans as certain active compounds (e.g. those with large molecular configuration) are only poorly absorbed in the gastrointestinal tract and/or may undergo metabolic degradation. Therefore experimental models are required which provide information if protective effects take place in humans under realistic conditions. Over the last years, several methods have been developed which are increasingly used in human intervention trials. The most widely used techniques are chemical determinations of oxidised guanosine in peripheral blood cells or urine and single cell gel electrophoresis (comet) assays with lymphocytes which are based on the measurement of DNA migration in an electric field. By using of DNA-restriction enzymes (formamidopyrimidine DNA glycosylase and endonuclease III) it is possible to monitor the endogenous formation of oxidised purines and pyrimidines; recently also protocols have been developed which enable to monitor alterations in the repair of oxidised DNA. Alternatively, also the frequency of micronucleated cells can be monitored with the cytokinesis block method in peripheral human blood cells before and after intervention with putative antioxidants. To obtain information on alterations of the sensitivity towards oxidative damage, the cells can be treated ex vivo with ROS (H(2)O(2) exposure, radiation). The evaluation of currently available human studies shows that in approximately half of them protective effects of dietary factors towards oxidative DNA-damage were observed. Earlier studies focused predominantly on the effects of vitamins (A, C, E) and carotenoids, more recently also the effects of fruit juices (from grapes, kiwi) and beverages (soy milk, tea, coffee), vegetables (tomato products, berries, Brussels sprouts) and other components of the human diet (coenzyme Q(10), polyunsaturated fatty acids) were investigated. On the basis of the results of these studies it was possible to identify dietary compounds which are highly active (e.g. gallic acid). At present, strong efforts are made to elucidate whether the different parameters of oxidative DNA-damage correlates with life span, cancer and other age related diseases. The new techniques are highly useful tools which provide valuable information if dietary components cause antioxidant effects in humans and can be used to identify individual protective compounds and also to develop nutritional strategies to reduce the adverse health effects of ROS.

Preliminary tests of silicon carbide based concretes for hybrid rocket nozzles in a solar furnace

NASA Astrophysics Data System (ADS)

D'Elia, Raffaele; Bernhart, Gérard; Cutard, Thierry; Peraudeau, Gilles; Balat-Pichelin, Marianne

2014-06-01

This research is part of the PERSEUS project, a space program concerning hybrid propulsion and supported by CNES. The main goal of this study is to characterise silicon carbide based micro-concrete with a maximum aggregates size of 800 μm, in a hybrid propulsion environment. The nozzle throat has to resist to a highly oxidising polyethylene (PE)/N2O hybrid environment, under temperatures ranging up to 2980 K. The study is divided into two main parts: the first one deals with the thermo-mechanical characterisation of the material up to 1500 K and the second one with an investigation on the oxidation behaviour in a standard atmosphere, under a solar flux up to 13.5 MW/m2. Young's modulus was determined by resonant frequency method: results show an increase with the stabilisation temperature. Four point bending tests have shown a rupture tensile strength increasing with stabilisation temperature, up to 1473 K. Sintering and densification processes are primary causes of this phenomenon. Visco-plastic behaviour appears at 1373 K, due to the formation of liquid phases in cement ternary system. High-temperature oxidation in ambient air was carried out at PROMES-CNRS laboratory, on a 2 kW solar furnace, with a concentration factor of 15,000. A maximum 13.5 MW/m2 incident solar flux and a 7-90 s exposure times have been chosen. Optical microscopy, SEM, EDS analyses were used to determine the microstructure evolution and the mass loss kinetics. During these tests, silicon carbide undergoes active oxidation with production of SiO and CO smokes and ablation. A linear relation between mass loss and time is found. Oxidation tests performed at 13.5 MW/m2 solar flux have shown a mass loss of 10 mg/cm2 after 15 s. After 90 s, the mass loss reaches 60 mg/cm2. Surface temperature measurement is a main point in this study, because of necessity of a thermo-mechanical-ablative model for the material. Smokes appear at around 5.9 MW/m2, leading to the impossibility of useful temperature measurements by optical pyrometry. Micro-concrete is really interesting for the nozzle realisation, thanks to its workability, and its thermo-mechanical properties. After 30 s, mass loss in micro-concrete is one half of pure α-SiC. This result is really interesting to study SiC-based concretes in oxidising environments, instead of sintered α-SiC.

Synthesis and characterisation of the uranium pyrochlore betafite [(Ca,U)₂(Ti,Nb,Ta)₂O₇].

PubMed

McMaster, Scott A; Ram, Rahul; Charalambous, Fiona; Pownceby, Mark I; Tardio, James; Bhargava, Suresh K

2014-09-15

Betafite of composition [(Ca,U)2(Ti,Nb,Ta)2O7] was prepared via a solid state synthesis route. The synthesis was shown to be sensitive to initial reactant ratios, the atmosphere used (oxidising, neutral, reducing) and time. The optimum conditions for the synthesis of betafite were found to be heating the reactants required at 1150°C for 48 h under an inert gas atmosphere. XRD characterisation revealed that the synthesised betafite contained minor impurities. EPMA analysis of a sectioned surface showed very small regions of Ca-free betafite on grain boundaries as well as minor rutile impurities. Some heterogeneity between the Nb:Ta ratio was observed by quantitative EPMA but was generally within the nomenclature requirements stated for betafite. SEM analysis revealed the synthesised betafite was comprised mostly of hexaoctohedral crystals of ∼ 3 μm in diameter. XPS analysis of the sample showed that the uranium in the synthesised betafite was predominately present in the U(5+) oxidation state. A minor amount of U(6+) was also detected which was possibly due to surface oxidation. Copyright © 2014 Elsevier B.V. All rights reserved.

The nature of organic records in impact excavated rocks on Mars

NASA Astrophysics Data System (ADS)

Montgomery, W.; Bromiley, G. D.; Sephton, M. A.

2016-08-01

Impact ejected rocks are targets for life detection missions to Mars. The Martian subsurface is more favourable to organic preservation than the surface owing to an attenuation of radiation and physical separation from oxidising materials with increasing depth. Impact events bring materials to the surface where they may be accessed without complicated drilling procedures. On Earth, different assemblages of organic matter types are derived from varying depositional environments. Here we assess whether these different types of organic materials can survive impact events without corruption. We subjected four terrestrial organic matter types to elevated pressures and temperatures in piston-cylinder experiments followed by chemical characterisation using whole-rock pyrolysis-gas chromatography-mass spectrometry. Our data reveal that long chain hydrocarbon-dominated organic matter (types I and II; mainly microbial or algal) are unresistant to pressure whereas aromatic hydrocarbon-dominated organic matter types (types III and IV; mainly land plant, metamorphosed or degraded, displaying some superficial chemical similarities to abiotic meteoritic organic matter) are relatively resistant. This suggests that the impact excavated record of potential biology on Mars will be unavoidably biased, with microbial organic matter underrepresented while metamorphosed, degraded or abiotic meteoritic organic matter types will be selectively preserved.

The nature of organic records in impact excavated rocks on Mars.

PubMed

Montgomery, W; Bromiley, G D; Sephton, M A

2016-08-05

Impact ejected rocks are targets for life detection missions to Mars. The Martian subsurface is more favourable to organic preservation than the surface owing to an attenuation of radiation and physical separation from oxidising materials with increasing depth. Impact events bring materials to the surface where they may be accessed without complicated drilling procedures. On Earth, different assemblages of organic matter types are derived from varying depositional environments. Here we assess whether these different types of organic materials can survive impact events without corruption. We subjected four terrestrial organic matter types to elevated pressures and temperatures in piston-cylinder experiments followed by chemical characterisation using whole-rock pyrolysis-gas chromatography-mass spectrometry. Our data reveal that long chain hydrocarbon-dominated organic matter (types I and II; mainly microbial or algal) are unresistant to pressure whereas aromatic hydrocarbon-dominated organic matter types (types III and IV; mainly land plant, metamorphosed or degraded, displaying some superficial chemical similarities to abiotic meteoritic organic matter) are relatively resistant. This suggests that the impact excavated record of potential biology on Mars will be unavoidably biased, with microbial organic matter underrepresented while metamorphosed, degraded or abiotic meteoritic organic matter types will be selectively preserved.

The nature of organic records in impact excavated rocks on Mars

PubMed Central

Montgomery, W.; Bromiley, G. D.; Sephton, M. A.

2016-01-01

Impact ejected rocks are targets for life detection missions to Mars. The Martian subsurface is more favourable to organic preservation than the surface owing to an attenuation of radiation and physical separation from oxidising materials with increasing depth. Impact events bring materials to the surface where they may be accessed without complicated drilling procedures. On Earth, different assemblages of organic matter types are derived from varying depositional environments. Here we assess whether these different types of organic materials can survive impact events without corruption. We subjected four terrestrial organic matter types to elevated pressures and temperatures in piston-cylinder experiments followed by chemical characterisation using whole-rock pyrolysis-gas chromatography-mass spectrometry. Our data reveal that long chain hydrocarbon-dominated organic matter (types I and II; mainly microbial or algal) are unresistant to pressure whereas aromatic hydrocarbon-dominated organic matter types (types III and IV; mainly land plant, metamorphosed or degraded, displaying some superficial chemical similarities to abiotic meteoritic organic matter) are relatively resistant. This suggests that the impact excavated record of potential biology on Mars will be unavoidably biased, with microbial organic matter underrepresented while metamorphosed, degraded or abiotic meteoritic organic matter types will be selectively preserved. PMID:27492071

Cytochrome bo(3) from Escherichia coli: the binding and turnover of nitric oxide.

PubMed

Butler, Clive; Forte, Elena; Maria Scandurra, Francesca; Arese, Marzia; Giuffré, Alessandro; Greenwood, Colin; Sarti, Paolo

2002-09-06

The reaction of nitric oxide (NO) with fast and reduced cytochrome bo(3)(cyt bo(3)) from Escherichia coli has been investigated. The stoichiometry of NO binding to cyt bo(3) was determined using an NO electrode in the [NO] range 1-14 microM. Under reducing conditions, the initial decrease in [NO] following the addition of cyt bo(3) corresponded to binding of 1 NO molecule per cyt bo(3) functional unit. After this "rapid" NO binding phase, there was a slow, but significant rate of NO consumption ( approximately 0.3molNOmol bo(3)(-1)min(-1)), indicating that cyt bo(3) possesses a low level of NO reductase activity. The binding of NO to fast pulsed enzyme was also investigated. The results show that in the [NO] range used (1-14 microM) both fast and pulsed oxidised cyt bo(3) bind NO with a stoichiometry of 1:1 with an observed dissociation constant of K(d)=5.6+/-0.6 microM and that NO binding was inhibited by the presence of Cl(-). The binding of nitrite to the binuclear centre causes spectral changes similar to those observed upon NO binding to fast cyt bo(3). These results are discussed in relation to the model proposed by Wilson and co-workers [FEBS Lett. 414 (1997) 281] where the binding of NO to Cu(B)(II) results in the formation of the nitrosonium (Cu(B)(I)-NO(+)) complex. NO(+) then reacts with OH(-), a Cu(B) ligand, to form nitrite, which can bind at the binuclear centre. This work suggests for the first time that the binding of NO to oxidised cyt bo(3) does result in the reduction of Cu(B).

Newer antiatherosclerosis treatment strategies.

PubMed

Aggarwal, Amitesh; Singh, Safal

2011-01-01

Atherosclerosis has been a target of much clinical and molecular research. As a result of this extensive research, it is amply clear that atherogenesis is a multifactorial process involving an interplay of metabolic, immune and inflammatory mechanisms. Antiatherosclerotic strategies are today aiming for a multipronged approach targeting each arm of this multifactorial process. The newer agents under development can be divided into three broad categories: anti-inflammatory agents, modulators of intermediary metabolism and antiatherosclerosis vaccines. Potential targets for anti-inflammatory agents include inhibition of conversion of low-density lipoprotein (LDL) to oxidised LDL, blocking or downregulation of cell adhesion molecules, chemokine modulation and macrophage receptor blockade. Beyond inhibition of plaque formation, efforts are also ongoing to develop agents which stabilise the plaque by increasing its fibrous content and inhibiting its disruption. So far as research in the sphere of intermediary metabolism is concerned, the focus is now primarily on raising high-density lipoprotein and promoting reverse cholesterol transport; potential targets include cholesteryl ester transfer protein, liver X-receptor, lecithin cholesterol acyltransferase and high-density lipoprotein mimetics. Acyl-coenzymeA: cholesterol acyltransferase is another enzyme whose selective and differential inhibition is under active investigation. The concept of immunisation against a non-communicable disease such as atherosclerosis is still in its nascent stages. However, with increasing evidence to suggest the role of antigen-specific T-cell-mediated immunity in atherogenesis, this approach is potentially promising. Possible antigens under evaluation include oxidised LDL and its subparticles, heat-shock proteins and cholesteryl ester transfer protein. With cardiovascular disease being the single leading cause of death worldwide, the development of a safe and successful antiatherosclerosis strategy (possibly employing a combination of agents acting at various levels) will indeed be a major 21st-century achievement.

Rapid aqueous phase SO2 oxidation in winter fog in the Indo-Gangetic Plain

NASA Astrophysics Data System (ADS)

Sachan, Himanshu; Sarkar, Chinmoy; Sinha, Baerbel

2013-04-01

Sulphate and sulphur dioxide play an important role in environmental chemistry and climate. The majority of anthropogenic sulphur is released directly as SO2, and a significant fraction of biogenic and natural sulphur emissions are also either directly released as SO2 or oxidised to SO2 in the atmosphere (e.g. H2S, OCS, DMS). Around 50% of global atmospheric sulphur dioxide is then oxidised to sulphate, while the rest is lost through dry and wet deposition. The pathway by which SO2 is oxidised to sulphate is critical in determining the climate forcing and environmental effects of sulphate. Gas-phase oxidation of SO2 by OH radicals or criegee intermediates produces H2SO4 (g), which plays an important role in controlling new particle formation in the troposphere and also modifies the surface properties of hydrophobic particles such as soot and mineral dust. Heterogeneous oxidation of SO2 is considered to occur primarily in cloud droplets, although oxidation on sea salt aerosols and mineral dust surfaces are considered to be regionally important. Heterogeneous oxidation leads to the formation of fewer and larger particles with shorter atmospheric lifetime. The major oxidation pathways which are considered to contribute to sulphate formation in the aqueous phase are oxidation by H2O2 and oxidation by O3 and the lifetime of SO2 with respect to all known loss processes combined is considered to be 1-2 days. Here we report measurements of SO2 measurements from IISER Mohali - Ambient Air Quality Station (30.67°N, 76.73°E), a station located at a suburban site in the Indo Gangetic Basin (IGB) during wintertime (10th Dec. 2011 to 29th Feb. 2012). We use a strong point source of SO2 with known SO2/CO emission ratio (brick kiln) located 6.5 km east of our measurement site to estimate the loss rate of SO2 in wintertime fog in the IGB. We consider the transport from the source to the receptor site to be Lagrangian and use the measured CO concentration at the receptors site to account for changes in the emission intensity (activity pattern) and the dilution of the plume during transport. We see a linear correlation between the measured SO2/CO ratio and the transport time. Binning the data on the basis of relative humidity and applying first order kinetics to SO2 loss within each humidity bin we find the SO2 loss rate with respect to aqueous phase oxidation at our sites varies between > 2.2 x 10-3 mol/cm3/s at 96 % RH and 3.8 x 10-4 mol/cm3/s at 47 % RH. Simple box model calculations reveal that neither oxidation by H2O2 nor oxidation by O3 can account for such rapid SO2 oxidation in the fog water. Considering the high mineral dust loadings are our station (PM 10 typically > 300 μg/m3) we propose that transition metal catalysis by TMI leached from natural mineral dust and resuspended road dust may be responsible for the rapid oxidation of SO2 in the fog water. However, the observed lifetime with respect to aqueous phase oxidation in wintertime fog is a factor 150-800 times shorter than the lifetime of SO2 with respect to TMI catalyzed oxidation currently implemented in global atmospheric chemistry models. During 2012-2013 winter season we will measure TMI concentrations in the fog water and verify the rates coefficients estimated from the ambient observation by conducting controlled experiments both using collected fog water and different TMI mixtures. If confirmed through laboratory studies our findings have major implications for the SO2 lifetime over the IGP (and possibly other regions with high mineral dust loadings) and will significantly alter the regional direct and indirect aerosol forcing estimates due to anthropogenic SO2 emissions. Acknowledgement: We thank the IISER Mohali Atmospheric Chemistry Facility for data and the Ministry of Human Resource Development (MHRD), India and IISER Mohali for funding the facility. Himanshu acknowledges the DST-INSPIRE Fellowship program. Chinmoy Sarkar thanks the Max Planck-DST India Partner Group on Tropospheric OH reactivity and VOCs for funding the research.

Fractography evolution in accelerated aging of UHMWPE after gamma irradiation in air.

PubMed

Medel, F; Gómez-Barrena, E; García-Alvarez, F; Ríos, R; Gracia-Villa, L; Puértolas, J A

2004-01-01

We studied the fracture surface evolution of ultra high molecular weight polyethylene (UHMWPE) specimens, manufactured from GUR 1050 compression moulded sheets, after gamma sterilisation in air followed by different aging times after thermal treatment at 120 degrees C. Degradation profiles were obtained by FTIR and DSC measurements after 0, 7, 14, 24 and 36h aging. We observed by SEM the morphology patterns at these aging times, in surface fractographies after uniaxial tensile test of standardised samples. The results pointed out clear differences between short and long aging times. At shorter times, 7h, the behaviour was similar to non-degraded UHMWPE, exhibiting ductile behaviour. At longer times, 24-36h, this thermal protocol provided a highly degraded zone in the subsurface, similar to the white band found after gamma irradiation in air followed by natural aging, although closer to the surface, at 150-200mum. The microstructure of this oxidation zone, similarly found in gamma irradiated samples shelf-aged for 6-7 years, although with different distribution of microvoids, was formed by fibrils, associated with embrittlement of the oxidised UHMWPE. In addition, the evolution of the oxidation index, the enthalpy content, the mechanical parameters, and the depth of the oxidation front deduced from the fractographies versus aging time showed that a changing behaviour in the degradation rate appeared at intermediate aging times.

Metagenomic analysis of a desulphurisation system used to treat biogas from vinasse methanisation.

PubMed

Dias, Marcela França; Colturato, Luis Felipe; de Oliveira, João Paulo; Leite, Laura Rabelo; Oliveira, Guilherme; Chernicharo, Carlos Augusto; de Araújo, Juliana Calabria

2016-04-01

We investigated the response of microbial community to changes in H2S loading rate in a microaerated desulphurisation system treating biogas from vinasse methanisation. H2S removal efficiency was high, and both COD and DO seemed to be important parameters to biomass activity. DGGE analysis retrieved sequences of sulphide-oxidising bacteria (SOB), such as Thioalkalimicrobium sp. Deep sequencing analysis revealed that the microbial community was complex and remained constant throughout the experiment. Most sequences belonged to Firmicutes and Proteobacteria, and, to a lesser extent, Bacteroidetes, Chloroflexi, and Synergistetes. Despite the high sulphide removal efficiency, the abundance of the taxa of SOB was low, and was negatively affected by the high sulphide loading rate. Copyright © 2016 Elsevier Ltd. All rights reserved.

Pottery from a Chimú Workshop Studied by Mössbauer Spectroscopy

NASA Astrophysics Data System (ADS)

Tschauner, H.; Wagner, U.

2003-09-01

Ceramic finds from a pottery workshop in the Lambayeque valley were studied by neutron activation analysis, Mössbauer spectroscopy and X-ray diffraction in an attempt to assess an advanced division of labour on the North Coast of Peru during the Chimú period (AD 1350-1460). The study suggests that the material was predominantly fired in a reducing environment with partial reoxidation at the end of the firing cycles, although firing in an oxidising atmosphere has taken place occasionally. The observed variation of firing conditions is characteristic for the use of pit kilns. The results of the archaeometric studies confirm the stylistic studies and show that pottery was no status symbol and far less important as a carrier of Chimú style than metal artefacts.

Fish odor syndrome.

PubMed

Rehman, H U

1999-08-01

Fish odour syndrome (trimethylaminuria) is a metabolic syndrome caused by abnormal excretion of trimethylamine in the breath, urine, sweat, saliva and vaginal secretions. Trimethylamine is derived from the intestinal bacterial degradation of foods rich in choline and carnitine and is normally oxidised by the liver to odorless trimethylamine N-oxide which is then excreted in the urine. Impaired oxidation of trimethylamine is thought to be the cause of the fish odour syndrome and is responsible for the smell of rotting fish. Certain foods rich in choline exacerbate the condition and the patients have a variety of psychological problems. Recognition of the condition is important as dietary adjustments reduce the excretion of trimethylamine and may reduce the odour. Occasionally, a short course of metronidazole, neomycin and lactulose may suppress production of trimethylamine by reducing the activity of gut microflora.

Lipoic acid mitigates oxidative stress and recovers metabolic distortions in salt-stressed wheat seedlings by modulating ion homeostasis, the osmo-regulator level and antioxidant system.

PubMed

Gorcek, Zeynep; Erdal, Serkan

2015-11-01

Soil salinity is one of the most detrimental environmental factors affecting the growth of plants and limiting their agricultural productivity. This study investigated whether exogenous lipoic acid (LA) pretreatment plays a role in promoting salt tolerance in wheat seedlings. The seedlings were treated with LA (1.75 mmol L(-1)) and salt (100 mmol L(-1) NaCl) separately and a combination of them. Salt stress significantly reduced relative water content, leaf surface area, ribulose bisphosphate carboxylase expression, and chlorophyll content but increased the content of osmo-regulator protein, carbohydrates and proline. In addition, salinity led to an imbalance in the inorganic composition of wheat leaves. While it elevated Na(+) content compared to control, Ca content and K(+)/Na(+) ratio were reduced. Under saline conditions, despite increases in antioxidant enzyme activity and levels of antioxidant compounds (ascorbate and glutathione), the content of reactive oxygen species (superoxide anion, hydrogen peroxide) and malondialdehyde were higher than in control seedlings. LA significantly promoted osmo-regulator level and antioxidant enzyme activities compared to stressed seedlings alone. Also, it both increased levels of ascorbate and glutathione and regenerated their oxidised forms, thus contributing to maintaining cellular redox status. Similarly, LA prevented excessive accumulation of Na(+) and promoted K(+)/Na(+) ratio and Ca content. Reactive oxygen species content was significantly reduced, and the inhibitions in the above parameters markedly recovered. LA reduced salinity-induced oxidative damage and thus contributed to the growth and development of plants in saline soils by modulating ion homeostasis between plant and soil as well as in osmo-regulator content and antioxidant system. © 2014 Society of Chemical Industry.

A Burke-Schumann analysis of diffusion-flame structures supported by a burning droplet

NASA Astrophysics Data System (ADS)

Nayagam, Vedha; Dietrich, Daniel L.; Williams, Forman A.

2017-07-01

A Burke-Schumann description of three different regimes of combustion of a fuel droplet in an oxidising atmosphere, namely the premixed-flame regime, the partial-burning regime and the diffusion-flame regime, is presented by treating the fuel and oxygen leakage fractions through the flame as known parameters. The analysis shows that the burning-rate constant, the flame-standoff ratio, and the flame temperature in these regimes can be obtained from the classical droplet-burning results by suitable definitions of an effective ambient oxygen mass fraction and an effective fuel concentration in the droplet interior. The results show that increasing oxygen leakage alone through the flame lowers both the droplet burning rate and the flame temperature, whereas leakage of fuel alone leaves the burning rate unaffected while reducing the flame temperature and moving the flame closer to the droplet surface. Solutions for the partial-burning regime are shown to exist only for a limited range of fuel and oxygen leakage fractions.

Determination of nitrites in water by in-electrode coulometric titration in reticulated vitreous carbon electrode.

PubMed

Lenghartova, Katarina; Lauko, Lukas; Cachob, Frantisek; Beinrohr, Ernest

2015-01-01

Nitrite in water samples was determined by in-electrode coulometric titration in a reticulated vitreous carbon (RVC) electrode of 100 ppi porosity. The sample was mixed with dilute sulphuric acid and sodium sulphate, filled into a flow cell with the porous electrode and nitrite was oxidised to nitrate by constant current of 5 µA at which the potential of the electrode was monitored. The limits of detection and quantification were found to be 0.4 and 1.2 µg/L, respectively. The repeatability and reproducibility were 2.2 % and 2.6 %, respectively. The bias at 100 µg/L were found to be 0.3 %. The duration of the measurement is 2-3 min depending on the nitrite concentration. There were few interferences only, neutral and cationic surfactants decreased and increased slightly the signal, respectively. Humic acids above 30 mg/L increased the signal by 10 %. Drinking and surface water samples were analysed and the results matched well those from the photometric method.

Ecosystem responses to reduced and oxidised nitrogen inputs in European terrestrial habitats.

PubMed

Stevens, Carly J; Manning, Pete; van den Berg, Leon J L; de Graaf, Maaike C C; Wamelink, G W Wieger; Boxman, Andries W; Bleeker, Albert; Vergeer, Philippine; Arroniz-Crespo, Maria; Limpens, Juul; Lamers, Leon P M; Bobbink, Roland; Dorland, Edu

2011-03-01

While it is well established that ecosystems display strong responses to elevated nitrogen deposition, the importance of the ratio between the dominant forms of deposited nitrogen (NH(x) and NO(y)) in determining ecosystem response is poorly understood. As large changes in the ratio of oxidised and reduced nitrogen inputs are occurring, this oversight requires attention. One reason for this knowledge gap is that plants experience a different NH(x):NO(y) ratio in soil to that seen in atmospheric deposits because atmospheric inputs are modified by soil transformations, mediated by soil pH. Consequently species of neutral and alkaline habitats are less likely to encounter high NH(4)(+) concentrations than species from acid soils. We suggest that the response of vascular plant species to changing ratios of NH(x):NO(y) deposits will be driven primarily by a combination of soil pH and nitrification rates. Testing this hypothesis requires a combination of experimental and survey work in a range of systems. Copyright © 2010 Elsevier Ltd. All rights reserved.

Biomarker-indicated extent of oxidation of plant-derived organic carbon (OC) in relation to geomorphology in an arsenic contaminated Holocene aquifer, Cambodia.

PubMed

Magnone, Daniel; Richards, Laura A; Polya, David A; Bryant, Charlotte; Jones, Merren; van Dongen, Bart E

2017-10-12

The poisoning of rural populations in South and Southeast Asia due to high groundwater arsenic concentrations is one of the world's largest ongoing natural disasters. It is important to consider environmental processes related to the release of geogenic arsenic, including geomorphological and organic geochemical processes. Arsenic is released from sediments when iron-oxide minerals, onto which arsenic is adsorbed or incorporated, react with organic carbon (OC) and the OC is oxidised. In this study we build a new geomorphological framework for Kandal Province, a highly studied arsenic affected region of Cambodia, and tie this into wider regional environmental change throughout the Holocene. Analyses shows that the concentration of OC in the sediments is strongly inversely correlated to grainsize. Furthermore, the type of OC is also related to grain size with the clay containing mostly (immature) plant derived OC and sand containing mostly thermally mature derived OC. Finally, analyses indicate that within the plant derived OC relative oxidation is strongly grouped by stratigraphy with the older bound OC more oxidised than younger OC.

A review of the high temperature oxidation of uranium oxides in molten salts and in the solid state to form alkali metal uranates, and their composition and properties

NASA Astrophysics Data System (ADS)

Griffiths, Trevor R.; Volkovich, Vladimir A.

An extensive review of the literature on the high temperature reactions (both in melts and in the solid state) of uranium oxides (UO 2, U 3O 8 and UO 3) resulting in the formation of insoluble alkali metal (Li to Cs) uranates is presented. Their uranate(VI) and uranate(V) compounds are examined, together with mixed and oxygen-deficient uranates. The reactions of uranium oxides with carbonates, oxides, per- and superoxides, chlorides, sulfates, nitrates and nitrites under both oxidising and non-oxidising conditions are critically examined and systematised, and the established compositions of a range of uranate(VI) and (V) compounds formed are discussed. Alkali metal uranates(VI) are examined in detail and their structural, physical, thermodynamic and spectroscopic properties considered. Chemical properties of alkali metal uranates(VI), including various methods for their reduction, are also reported. Errors in the current theoretical treatment of uranate(VI) spectra are identified and the need to develop routes for the preparation of single crystals is stressed.

Biodeterioration of the Cement Composites

NASA Astrophysics Data System (ADS)

Luptáková, Alena; Eštoková, Adriana; Mačingová, Eva; Kovalčíková, Martina; Jenčárová, Jana

2016-10-01

The destruction of natural and synthetic materials is the spontaneous and irreversible process of the elements cycling in nature. It can by accelerated or decelerated by physical, chemical and biological influences. Biological influences are represented by the influence of the vegetation and microorganisms (MO). The destruction of cement composites by different MO through the diverse mechanisms is entitled as the concrete biodeterioration. Several sulphur compounds and species of MO are involved in this complex process. Heterotrophic and chemolithotrophic bacteria together with fungi have all been found in samples of corroding cement composites. The MO involved in the process metabolise the presented sulphur compounds (hydrogen sulphide, elemental sulphur etc.) to sulphuric acid reacting with concrete. When sulphuric acid reacts with a concrete matrix, the first step involves a reaction between the acid and the calcium hydroxide forming calcium sulphate. This is subsequently hydrated to form gypsum, the appearance of which on the surface of concrete pipes takes the form of a white, mushy substance which has no cohesive properties. In the continuing attack, the gypsum would react with the calcium aluminate hydrate to form ettringite, an expansive product. The use supplementary cementing composite materials have been reported to improve the resistance of concrete to biodeterioration. The aim of this work was the study of the cement composites biodeterioration by the bacteria Acidithiobacillus thiooxidans. Experimental works were focused on the comparison of special cement composites and its resistance affected by the activities of used sulphur-oxidising

Nitrogen activation of carbon-encapsulated zero-valent iron nanoparticles and influence of the activation temperature on heavy metals removal

NASA Astrophysics Data System (ADS)

Bonaiti, Stefania; Calderon, Blanca; Collina, Elena; Lasagni, Marina; Mezzanotte, Valeria; Aracil, Ignacio; Fullana, Andrés

2017-05-01

Nanoparticles of zero-valent iron (nZVI) represent a promising agent for environmental remediation. This is due to their core-shell structure which presents the characteristics of both metallic and oxidised iron, leading to sorption and reductive precipitation of metal ions. Nevertheless, nZVI application presents some limitations regarding their rapid oxidation and aggregation in the media which leads to the delivery of the ions after some hours (the “aging effect”). To address these issues, modifications of nZVI structure and synthesis methods have been developed in the last years. The aging problem was solved by using nZVI encapsulated inside carbon spheres (CE-nZVI), synthetized through Hydrothermal Carbonization (HTC). Results showed high heavy metals removal percentage. Furthermore, CE-nZVI were activated with nitrogen in order to increase the metallic iron content. The aim of this study was to test CE-nZVI post-treated with nitrogen at different temperatures in heavy metals removal, demonstrating that the influence of the temperature was negligible in nanoparticles removal efficiency.

Mitochondrial thermogenesis and obesity.

PubMed

Gambert, Ségolène; Ricquier, Daniel

2007-11-01

Thermogenesis is activated at the expense of carbon molecules. Mitochondria play a dominant role in oxidation and parallel heat production since the recovery of oxidation energy is less than perfect. Recent data of mitochondriogenesis and mitochondrial thermogenesis may boost research into certain aspects of obesity. Recent studies have outlined the unexpected decreased thermogenesis that limits fat loss during prolonged food restriction. Activation of fat oxidation in skeletal muscle remains a strategy against fat accumulation, however. Certain adipose depots have the potential to promote thermogenesis, either using mitochondrial uncoupling protein or independently. Peroxisome proliferator-activated receptor gamma coactivators alpha and ss are important regulators of mitochondria thermogenesis. Brain mitochondria are involved in the control of refeeding after starvation. This dual action of mitochondria inform their role in thermogenesis and energy partitioning. The importance of thyroid hormones in mitochondria thermogenesis is also confirmed. The clinical and research implications of these findings are that the mechanisms inhibiting adaptive thermogenesis during diet restriction should be investigated. An important field of research is the contribution of transcriptional coactivators to adipocyte plasticity since adipocytes have an underestimated ability to oxidise fatty acids in addition to their role in triglyceride storage.

Genotoxicity of TiO2 nanoparticles assessed by mini-gel comet assay and micronucleus scoring with flow cytometry.

PubMed

Di Bucchianico, Sebastiano; Cappellini, Francesca; Le Bihanic, Florane; Zhang, Yuning; Dreij, Kristian; Karlsson, Hanna L

2017-01-01

The widespread production and use of nanoparticles calls for faster and more reliable methods to assess their safety. The main aim of this study was to investigate the genotoxicity of three reference TiO 2 nanomaterials (NM) within the frame of the FP7-NANoREG project, with a particular focus on testing the applicability of mini-gel comet assay and micronucleus (MN) scoring by flow cytometry. BEAS-2B cells cultured under serum-free conditions were exposed to NM100 (anatase, 50-150nm), NM101 (anatase, 5-8nm) and NM103 (rutile, 20-28nm) for 3, 24 or 48h mainly at concentrations 1-30 μg/ml. In the mini-gel comet assay (eight gels per slide), we included analysis of (i) DNA strand breaks, (ii) oxidised bases (Fpg-sensitive sites) and (iii) light-induced DNA damage due to photocatalytic activity. Furthermore, MN assays were used and we compared the results of more high-throughput MN scoring with flow cytometry to that of cytokinesis-block MN cytome assay scored manually using a microscope. Various methods were used to assess cytotoxic effects and the results showed in general no or low effects at the doses tested. A weak genotoxic effect of the tested TiO 2 materials was observed with an induction of oxidised bases for all three materials of which NM100 was the most potent. When the comet slides were briefly exposed to lab light, a clear induction of DNA strand breaks was observed for the anatase materials, but not for the rutile. This highlights the risk of false positives when testing photocatalytically active materials if light is not properly avoided. A slight increase in MN formation for NM103 was observed in the different MN assays at the lower doses tested (1 and 5 μg/ml). We conclude that mini-gel comet assay and MN scoring using flow cytometry successfully can be used to efficiently study cytotoxic and genotoxic properties of nanoparticles. © The Author 2016. Published by Oxford University Press on behalf of the UK Environmental Mutagen Society.

Genotoxicity of TiO2 nanoparticles assessed by mini-gel comet assay and micronucleus scoring with flow cytometry

PubMed Central

Di Bucchianico, Sebastiano; Cappellini, Francesca; Le Bihanic, Florane; Zhang, Yuning; Dreij, Kristian; Karlsson, Hanna L.

2017-01-01

The widespread production and use of nanoparticles calls for faster and more reliable methods to assess their safety. The main aim of this study was to investigate the genotoxicity of three reference TiO2 nanomaterials (NM) within the frame of the FP7-NANoREG project, with a particular focus on testing the applicability of mini-gel comet assay and micronucleus (MN) scoring by flow cytometry. BEAS-2B cells cultured under serum-free conditions were exposed to NM100 (anatase, 50–150nm), NM101 (anatase, 5–8nm) and NM103 (rutile, 20–28nm) for 3, 24 or 48h mainly at concentrations 1–30 μg/ml. In the mini-gel comet assay (eight gels per slide), we included analysis of (i) DNA strand breaks, (ii) oxidised bases (Fpg-sensitive sites) and (iii) light-induced DNA damage due to photocatalytic activity. Furthermore, MN assays were used and we compared the results of more high-throughput MN scoring with flow cytometry to that of cytokinesis-block MN cytome assay scored manually using a microscope. Various methods were used to assess cytotoxic effects and the results showed in general no or low effects at the doses tested. A weak genotoxic effect of the tested TiO2 materials was observed with an induction of oxidised bases for all three materials of which NM100 was the most potent. When the comet slides were briefly exposed to lab light, a clear induction of DNA strand breaks was observed for the anatase materials, but not for the rutile. This highlights the risk of false positives when testing photocatalytically active materials if light is not properly avoided. A slight increase in MN formation for NM103 was observed in the different MN assays at the lower doses tested (1 and 5 μg/ml). We conclude that mini-gel comet assay and MN scoring using flow cytometry successfully can be used to efficiently study cytotoxic and genotoxic properties of nanoparticles. PMID:27382040

The effect of iron on montmorillonite stability. (II) Experimental investigation

NASA Astrophysics Data System (ADS)

Wilson, James; Cressey, Gordon; Cressey, Barbara; Cuadros, Javier; Ragnarsdottir, K. Vala; Savage, David; Shibata, Masahiro

2006-01-01

Several designs proposed for high-level nuclear waste (HLW) repositories include steel waste canisters surrounded by montmorillonite clay. This work investigates montmorillonite stability in the presence of native Fe, magnetite and aqueous solutions under hydrothermal conditions. Two series of experiments were conducted. In the first, mixtures of Na-montmorillonite, magnetite, native Fe, calcite, and NaCl solutions were reacted at 250 °C, Psat for between 93 and 114 days. In the second series, the starting mixtures included Na-montmorillonite, native Fe and solutions of FeCl 2 which were reacted at temperatures of 80, 150, and 250 °C, Psat, for 90-92 days. Experiments were analysed using XRD, FT-IR, TEM, ICP-AES, and ICP-MS. In the first series of experiments, native Fe oxidised to produce magnetite and the starting montmorillonite material was transformed to Fe-rich smectite only when the Fe was added predominantly as Fe metal rather than Fe oxide (magnetite). The Fe-rich smectite was initially Fe(II)-rich, which oxidised to produce an Fe(III)-rich form on exposure to air. The expansion of this material on ethylene glycol solvation was much reduced compared to the montmorillonite starting material. TEM imaging shows that partial loss of tetrahedral sheets occurred during transformation of the montmorillonite, resulting in adjacent layers becoming H-bonded with a 7 Å repeat. The reduced swelling property of the Fe-smectite product may be due predominantly to the structural disruption of smectite layers and the formation of H-bonds. Solute activities corresponded to the approximate stability field calculated for hypothetical Fe(II)-saponite. In the second series of experiments, significant smectite alteration was only observed at 250 °C and the product contained a small proportion of a 7 Å repeat structure, observable by XRD. In these experiments, solute activities coincide with berthierine. The experiments indicate that although bentonite is still a desirable choice of backfill material for HLW repositories, some loss of expandability may result if montmorillonite is altered to Fe-rich smectite at the interface between steel canisters and bentonite.

Exercise redox biochemistry: Conceptual, methodological and technical recommendations.

PubMed

Cobley, James N; Close, Graeme L; Bailey, Damian M; Davison, Gareth W

2017-08-01

Exercise redox biochemistry is of considerable interest owing to its translational value in health and disease. However, unaddressed conceptual, methodological and technical issues complicate attempts to unravel how exercise alters redox homeostasis in health and disease. Conceptual issues relate to misunderstandings that arise when the chemical heterogeneity of redox biology is disregarded: which often complicates attempts to use redox-active compounds and assess redox signalling. Further, that oxidised macromolecule adduct levels reflect formation and repair is seldom considered. Methodological and technical issues relate to the use of out-dated assays and/or inappropriate sample preparation techniques that confound biochemical redox analysis. After considering each of the aforementioned issues, we outline how each issue can be resolved and provide a unifying set of recommendations. We specifically recommend that investigators: consider chemical heterogeneity, use redox-active compounds judiciously, abandon flawed assays, carefully prepare samples and assay buffers, consider repair/metabolism, use multiple biomarkers to assess oxidative damage and redox signalling. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Oxidation of methane over palladium catalysts: effect of the support.

PubMed

Escandón, Lara S; Ordóñez, Salvador; Vega, Aurelio; Díez, Fernando V

2005-01-01

This work is focused on the deep catalytic oxidation of methane over supported palladium catalysts. The influences of the metal loading, oxidation state of palladium, nature of supports, presence of promoters in the supports (for zirconia-based supports), and thermal stability have been studied experimentally. Catalysts were prepared by incipient wetness of commercially available supports with aqueous solutions of palladium nitrate. For gamma-alumina support, it was observed that the optimal amount of palladium is between 0.5% and 2%, with higher amounts leading to a loss in specific activity. Concerning the oxidation state of the catalyst, it is concluded that for all the supports tested in the present work, a reduction of the catalyst is not needed, yielding the same conversion at steady state catalysts reduced and oxidised. The thermal stability of various supported catalysts were also studied, zirconia supports being the most active. These supports, specially Y-modified zirconia support, do not suffer appreciable deactivation below 500 degrees C.

Iron isotopes in ancient and modern komatiites: Evidence in support of an oxidised mantle from Archean to present

NASA Astrophysics Data System (ADS)

Hibbert, K. E. J.; Williams, H. M.; Kerr, A. C.; Puchtel, I. S.

2012-03-01

The mantle of the modern Earth is relatively oxidised compared to the initially reducing conditions inferred for core formation. The timing of the oxidation of the mantle is not conclusively resolved but has important implications for the timing of the development of the hydrosphere and atmosphere. In order to examine the timing of this oxidation event, we present iron isotope data from three exceptionally well preserved komatiite localities, Belingwe (2.7 Ga), Vetreny (2.4 Ga) and Gorgona (0.089 Ga). Measurements of Fe isotope compositions of whole-rock samples are complemented by the analysis of olivine, spinel and pyroxene separates. Bulk-rock and olivine Fe isotope compositions (δ57Fe) define clear linear correlations with indicators of magmatic differentiation (Mg#, Cr#). The mean Fe isotope compositions of the 2.7-2.4 Ga and 0.089 Ga samples are statistically distinct and this difference can be explained by greater extent of partial melting represented by the older samples and higher mantle ambient temperatures in the Archean and early Proterozoic relative to the present day. Significantly, samples of all ages define continuous positive linear correlations between bulk rock δ57Fe and V/Sc and δ57Fe and V, and between V/Sc and V with TiO2, providing evidence for the incompatible behaviour of V (relative to Sc) and of isotopically heavy Fe. Partial melting models calculated using partition coefficients for V at oxygen fugacities (fO2s) of 0 and + 1 relative to the fayalite-magnetite-quartz buffer (FMQ) best match the data arrays, which are defined by all samples, from late Archean to Tertiary. These data, therefore, provide evidence for komatiite generation under moderately oxidising conditions since the late Archean, and argue against a change in mantle fO2 concomitant with atmospheric oxygenation at ~ 2.4 Ga.

Genome-Guided Analysis of Clostridium ultunense and Comparative Genomics Reveal Different Strategies for Acetate Oxidation and Energy Conservation in Syntrophic Acetate-Oxidising Bacteria

PubMed Central

Manzoor, Shahid; Schnürer, Anna; Müller, Bettina

2018-01-01

Syntrophic acetate oxidation operates close to the thermodynamic equilibrium and very little is known about the participating organisms and their metabolism. Clostridium ultunense is one of the most abundant syntrophic acetate-oxidising bacteria (SAOB) that are found in engineered biogas processes operating with high ammonia concentrations. It has been proven to oxidise acetate in cooperation with hydrogenotrophic methanogens. There is evidence that the Wood-Ljungdahl (WL) pathway plays an important role in acetate oxidation. In this study, we analysed the physiological and metabolic capacities of C. ultunense strain Esp and strain BST on genome scale and conducted a comparative study of all the known characterised SAOB, namely Syntrophaceticus schinkii, Thermacetogenium phaeum, Tepidanaerobacter acetatoxydans, and Pseudothermotoga lettingae. The results clearly indicated physiological robustness to be beneficial for anaerobic digestion environments and revealed unexpected metabolic diversity with respect to acetate oxidation and energy conservation systems. Unlike S. schinkii and Th. phaeum, C. ultunense clearly does not employ the oxidative WL pathway for acetate oxidation, as its genome (and that of P. lettingae) lack important key genes. In both of those species, a proton motive force is likely formed by chemical protons involving putative electron-bifurcating [Fe-Fe] hydrogenases rather than proton pumps. No genes encoding a respiratory Ech (energy-converting hydrogenase), as involved in energy conservation in Th. phaeum and S. schinkii, were identified in C. ultunense and P. lettingae. Moreover, two respiratory complexes sharing similarities to the proton-translocating ferredoxin:NAD+ oxidoreductase (Rnf) and the Na+ pumping NADH:quinone hydrogenase (NQR) were predicted. These might form a respiratory chain that is involved in the reduction of electron acceptors rather than protons. However, involvement of these complexes in acetate oxidation in C. ultunense and P. lettingae needs further study. This genome-based comparison provides a solid platform for future meta-proteomics and meta-transcriptomics studies and for metabolic engineering, control, and monitoring of SAOB. PMID:29690652

Flight Validation of the Thermal Propellant Gauging Method used at EADS Astrium

NASA Astrophysics Data System (ADS)

Dandaleix, L.; Ounougha, L.; Jallade, S.

2004-10-01

EADS Astrium recently met a major milestone in the field of propellant gauging with the first reorbitation of an Eurostar tanks equipped satellite. It proved successful determining the remaining available propellant mass for spacecraft displacement beyond the customer specified graveyard orbit; thus demonstrating its expertness in Propellant Gauging in correlation with tank residual mass minimization. A critical parameter in satellite operational planning is indeed the accurate knowledge of the on-board remaining propellant mass; basically for the commercial telecommunication missions, where it is the major criterion for lifetime maximization. To provide an accurate and reliable process for measurement of this propellant mass throughout lifetime, EADS Astrium uses a Combination of two independent techniques: The Dead Reckoning Method (maximum accuracy at BOL), based on thrusters flow rate prediction &the Thermal Propellant Gauging Technique, deriving the propellant mass from the tank thermal capacity (Absolute gauging method, with increasing accuracy along lifetime). Then, the present article shows the recent flight validation of the Gauging method obtained for Eurostar E2000 propellant tanks including the validation of the different thermodynamic models. ABBREVIATIONS &ACRONYMS BOL, MOL, EOL: Beginning, Middle &End of Life Cempty: Empty tank thermal inertia [J/K] Chelium: Helium thermal inertia [J/K] Cpropellant: Propellant thermal inertia [J/K] Ct = C1+C2: Total tank thermal inertia (Subscript for upper node and for lower node) [J/K] CPS: Combined Propulsion System DR: Dead Reckoning FM: Flight Model LAE: Liquid Apogee Engine lsb: Least significant byte M0: TPGS Uncertainty component linked to Cempty mox, mfuel: Propellant mass of oxidiser &fuel [kg] Pox, Pfuel: Pressure of oxidiser &fuel [bar] PTA: Propellant Tank Assembly Q: Heater power [W] Qox, Qfuel: Mass flow rate of oxidiser &fuel [kg/s] RCT: Reaction Control Thrusters T0: Spacecraft platform equilibrium temperature TPGS: Thermal Propellant Gauging Software TPGT: Thermal Propellant Gauging Technique T1i: Internal thermal gradients [K] T2i: External thermal gradients [K] Ï 1: Internal thermal characteristic time [s] 2: External thermal characteristic time [s

Genome-Guided Analysis of Clostridium ultunense and Comparative Genomics Reveal Different Strategies for Acetate Oxidation and Energy Conservation in Syntrophic Acetate-Oxidising Bacteria.

PubMed

Manzoor, Shahid; Schnürer, Anna; Bongcam-Rudloff, Erik; Müller, Bettina

2018-04-23

Syntrophic acetate oxidation operates close to the thermodynamic equilibrium and very little is known about the participating organisms and their metabolism. Clostridium ultunense is one of the most abundant syntrophic acetate-oxidising bacteria (SAOB) that are found in engineered biogas processes operating with high ammonia concentrations. It has been proven to oxidise acetate in cooperation with hydrogenotrophic methanogens. There is evidence that the Wood-Ljungdahl (WL) pathway plays an important role in acetate oxidation. In this study, we analysed the physiological and metabolic capacities of C. ultunense strain Esp and strain BS T on genome scale and conducted a comparative study of all the known characterised SAOB, namely Syntrophaceticus schinkii , Thermacetogenium phaeum , Tepidanaerobacter acetatoxydans , and Pseudothermotoga lettingae . The results clearly indicated physiological robustness to be beneficial for anaerobic digestion environments and revealed unexpected metabolic diversity with respect to acetate oxidation and energy conservation systems. Unlike S. schinkii and Th. phaeum , C. ultunense clearly does not employ the oxidative WL pathway for acetate oxidation, as its genome (and that of P. lettingae ) lack important key genes. In both of those species, a proton motive force is likely formed by chemical protons involving putative electron-bifurcating [Fe-Fe] hydrogenases rather than proton pumps. No genes encoding a respiratory Ech (energy-converting hydrogenase), as involved in energy conservation in Th. phaeum and S. schinkii, were identified in C. ultunense and P. lettingae . Moreover, two respiratory complexes sharing similarities to the proton-translocating ferredoxin:NAD⁺ oxidoreductase (Rnf) and the Na⁺ pumping NADH:quinone hydrogenase (NQR) were predicted. These might form a respiratory chain that is involved in the reduction of electron acceptors rather than protons. However, involvement of these complexes in acetate oxidation in C. ultunense and P. lettingae needs further study. This genome-based comparison provides a solid platform for future meta-proteomics and meta-transcriptomics studies and for metabolic engineering, control, and monitoring of SAOB.

Toward the next generation of air quality monitoring: Mercury

NASA Astrophysics Data System (ADS)

Pirrone, Nicola; Aas, Wenche; Cinnirella, Sergio; Ebinghaus, Ralf; Hedgecock, Ian M.; Pacyna, Jozef; Sprovieri, Francesca; Sunderland, Elsie M.

2013-12-01

Mercury is a global pollutant that is ubiquitous in the environment. Enrichment of mercury in the biosphere as the result of human activities and subsequent production of methylmercury (MeHg) has resulted in elevated concentrations in fish, wildlife and marine mammals globally. Elemental mercury (Hg0) is the most common form of mercury in the atmosphere, and the form that is most readily transported long distances from its emission source. Most mercury deposition from the atmosphere is in the highly soluble, oxidised inorganic form HgII. Thus, understanding atmospheric transport and oxidant distribution is essential for understanding mercury inputs to ecosystems. Methylmercury (MeHg) is the most toxic form of mercury that accumulates in aquatic food web and can cause a variety of negative health effects such as long-term IQ deficits and cardiovascular impairment in exposed individuals. Humans are predominately exposed to MeHg by consuming fish. Hg0 emitted from anthropogenic sources has a long (6 months-1 year) atmospheric residence time allowing it to be transported long distances in the atmosphere. It is eventually oxidised to the highly soluble HgII (likely by atomic Br and/or OH/O3) and rapidly deposited with precipitation. Some of the mercury deposited to terrestrial and marine ecosystems is converted to MeHg, which is the only form that bioaccumulates in aquatic food webs. Recent studies suggest that there is a first-order relationship between the supply of inorganic mercury to ecosystems and production of MeHg, thus implying that declines in deposition will translate directly into reduced concentrations in biota and human exposures. However, one of the major uncertainties in this cycle is the time scale required for these changes to take place and this is known to vary from years to centuries across different environmental compartments depending on their physical and biogeochemical attributes. Thus, a key challenge in the case of mercury pollution is understanding the link between the magnitude of mercury emissions and the concentrations found in the fish that we consume. For air quality monitoring, priorities include expanding the existing data collection network and widening the scope of atmospheric mercury measurements (elemental, oxidised, and particulate species as well as mercury in precipitation). Presently, the only accurate indicators of mercury impacts on human and biological health are methylmercury concentrations in biota. However, recent advances in analytical techniques (stable mercury isotopes) and integrated modelling tools are allowing greater understanding of the relationship between atmospheric deposition, concentrations in water, methylation and uptake by biota. This article recommends an expansion of the current atmospheric monitoring network and the establishment of new coordinated measurements of total mercury and methylmercury concentrations in seawater and concurrent concentrations and trends in marine fish.

β-Cyclodextrin functionalised gold nanoclusters as luminescence probes for the ultrasensitive detection of dopamine.

PubMed

Ban, Rui; Abdel-Halim, E S; Zhang, Jianrong; Zhu, Jun-Jie

2015-02-21

A novel luminescence probe based on mono-6-amino-β-cyclodextrin (NH2-β-CD) functionalised gold nanoclusters (β-CD-AuNC) was designed for dopamine (DA) detection. The NH2-β-CD molecules were conjugated onto the surface of 11-mercaptoundecanoic acid capped AuNCs (11-MUA-AuNC) via a carbodiimide coupling reaction. The integrity of the β-CD cavities was preserved on the surface of AuNCs and they retained their capability for molecular DA host-guest recognition. DA could be captured by the β-CD cavities to form an inclusion complex in which the oxidised DA could quench the fluorescence of the β-CD-AuNC probe by electron transfer. The probe could be used to quantify DA in the range of 5-1000 nM with a detection limit of 2 nM. This sensitivity was 1-2 orders of magnitude higher than that in previously reported methods. Interference by both ascorbic acid (AA) and uric acid (UA) was not observed. Therefore, the β-CD-AuNC probe could be directly used to determine the DA content in biological samples without further separation. This strategy was successfully applied to a DA assay in spiked human serum samples and it exhibited remarkable accuracy, sensitivity and selectivity.

The study of thin films on solid aerosol particles using optical trapping and Mie scattering from a broadband white LED

NASA Astrophysics Data System (ADS)

Jones, Stephanie H.; King, Martin D.; Ward, Andrew D.

2014-09-01

A counter-propagating optical trap has been used to study thin organic films on the surface of solid particles levitated in air. Micron sized silica spheres have been trapped in air between opposed 1064 nm laser beams, and illuminated with a broadband white LED. Backscattered light from the trapped particle was collected to obtain a Mie spectrum over the 495-670 nm wavelength range and this was used to determine particle radius and wavelength dependent refractive index (Jones et al., 2013). The trapped particle was coated using a flow of organic vapour and the resultant thin film analysed using a coated sphere model. Resonance positions in the Mie spectrum were monitored with time in order to determine film formation, thickness and refractive index. Whilst thin films are believed to form naturally on atmospheric aerosols (Tervahattu et al., 2002), a debate remains as to whether the organic component completely coats the aerosol surface or partially engulfs it. Such films are readily oxidised in the atmosphere causing a change in aerosol properties and knowledge of aerosol properties is required to understand their effect on the climate. The use of optical trapping combined with Mie spectra acquisition to study and characterise coated solid particles is therefore an important step in atmospheric science.

Hydrogen suppresses UO 2 corrosion

NASA Astrophysics Data System (ADS)

Carbol, Paul; Fors, Patrik; Gouder, Thomas; Spahiu, Kastriot

2009-08-01

Release of long-lived radionuclides such as plutonium and caesium from spent nuclear fuel in deep geological repositories will depend mainly on the dissolution rate of the UO 2 fuel matrix. This dissolution rate will, in turn, depend on the redox conditions at the fuel surface. Under oxidative conditions UO 2 will be oxidised to the 1000 times more soluble UO 2.67. This may occur in a repository as the reducing deep groundwater becomes locally oxidative at the fuel surface under the effect of α-radiolysis, the process by which α-particles emitted from the fuel split water molecules. On the other hand, the groundwater corrodes canister iron generating large amounts of hydrogen. The role of molecular hydrogen as reductant in a deep bedrock repository is questioned. Here we show evidence of a surface-catalysed reaction, taking place in the H 2-UO 2-H 2O system where molecular hydrogen is able to reduce oxidants originating from α-radiolysis. In our experiment the UO 2 surface remained stoichiometric proving that the expected oxidation of UO 2.00 to UO 2.67 due to radiolytic oxidants was absent. As a consequence, the dissolution of UO 2 stopped when equilibrium was reached between the solid phase and U 4+ species in the aqueous phase. The steady-state concentration of uranium in solution was determined to be 9 × 10 -12 M, about 30 times lower than previously reported for reducing conditions. Our findings show that fuel dissolution is suppressed by H 2. Consequently, radiotoxic nuclides in spent nuclear fuel will remain immobilised in the UO 2 matrix. A mechanism for the surface-catalysed reaction between molecular hydrogen and radiolytic oxidants is proposed.

Examination of Surface Deposits on Oldbury Reactor Core Graphite to Determine the Concentration and Distribution of 14C.

PubMed

Payne, Liam; Heard, Peter J; Scott, Thomas B

2016-01-01

Pile Grade A graphite was used as a moderator and reflector material in the first generation of UK Magnox nuclear power reactors. As all of these reactors are now shut down there is a need to examine the concentration and distribution of long lived radioisotopes, such as 14C, to aid in understanding their behaviour in a geological disposal facility. A selection of irradiated graphite samples from Oldbury reactor one were examined where it was observed that Raman spectroscopy can distinguish between underlying graphite and a surface deposit found on exposed channel wall surfaces. The concentration of 14C in this deposit was examined by sequentially oxidising the graphite samples in air at low temperatures (450°C and 600°C) to remove the deposit and then the underlying graphite. The gases produced were captured in a series of bubbler solutions that were analysed using liquid scintillation counting. It was observed that the surface deposit was relatively enriched with 14C, with samples originating lower in the reactor exhibiting a higher concentration of 14C. Oxidation at 600°C showed that the remaining graphite material consisted of two fractions of 14C, a surface associated fraction and a graphite lattice associated fraction. The results presented correlate well with previous studies on irradiated graphite that suggest there are up to three fractions of 14C; a readily releasable fraction (corresponding to that removed by oxidation at 450°C in this study), a slowly releasable fraction (removed early at 600°C in this study), and an unreleasable fraction (removed later at 600°C in this study).

Examination of Surface Deposits on Oldbury Reactor Core Graphite to Determine the Concentration and Distribution of 14C

PubMed Central

Payne, Liam; Heard, Peter J.; Scott, Thomas B.

2016-01-01

Pile Grade A graphite was used as a moderator and reflector material in the first generation of UK Magnox nuclear power reactors. As all of these reactors are now shut down there is a need to examine the concentration and distribution of long lived radioisotopes, such as 14C, to aid in understanding their behaviour in a geological disposal facility. A selection of irradiated graphite samples from Oldbury reactor one were examined where it was observed that Raman spectroscopy can distinguish between underlying graphite and a surface deposit found on exposed channel wall surfaces. The concentration of 14C in this deposit was examined by sequentially oxidising the graphite samples in air at low temperatures (450°C and 600°C) to remove the deposit and then the underlying graphite. The gases produced were captured in a series of bubbler solutions that were analysed using liquid scintillation counting. It was observed that the surface deposit was relatively enriched with 14C, with samples originating lower in the reactor exhibiting a higher concentration of 14C. Oxidation at 600°C showed that the remaining graphite material consisted of two fractions of 14C, a surface associated fraction and a graphite lattice associated fraction. The results presented correlate well with previous studies on irradiated graphite that suggest there are up to three fractions of 14C; a readily releasable fraction (corresponding to that removed by oxidation at 450°C in this study), a slowly releasable fraction (removed early at 600°C in this study), and an unreleasable fraction (removed later at 600°C in this study). PMID:27706228

Molecular characterization of the fatty alcohol oxidation pathway for wax-ester mobilization in germinated jojoba seeds

USDA-ARS?s Scientific Manuscript database

Jojoba (Simmondsia chinensis) is the only plant species known to use liquid wax esters (WE) as a primary seed storage reserve. Upon germination, WE hydrolysis releases very long-chain fatty alcohols, which must be oxidised to fatty acids by the sequential action of a fatty alcohol oxidase (FAO) and ...

[Skeletal muscles, physical activity and health].

PubMed

Saltin, B; Helge, J W

2000-11-01

The metabolic capacity of skeletal muscle plays a significant role for insulin sensitivity and the blood lipid profile. The metabolic capacity of the muscle is a function of the individual's physical activity level. This is also true for the content of type IIa muscle fibres, which is reduced, and the number of capillaries, which is elevated with muscle usage. Several of these skeletal muscle features are risk factors for or linked with life-style induced diseases such as type II diabetes, hypertension, hyperlipemia and obesity. The central role of the skeletal muscle and its functional metabolic capacity for life style diseases highlights the importance of people maintaining daily physical activity. This article focuses on the link between the metabolic capacity of skeletal muscle and the metabolic syndrome and briefly discusses the explanations for this relationship. As one important aspect if skeletal muscle has a high capacity for lipid oxidation, then more saturated fatty acids are oxidised and more unsaturated fatty acids are built in the phospholipid fraction of the plasma membrane, giving it more fluidity and improved insulin sensitivity. Moreover, the article points at the role of these fatty acids in activating genes via the PPAR-receptor system essential for enzyme and transport proteins in the lipid metabolism.

Bioelectro-Claus processes using MFC technology: Influence of co-substrate.

PubMed

Raschitor, A; Soreanu, G; Fernandez-Marchante, C M; Lobato, J; Cañizares, P; Cretescu, I; Rodrigo, M A

2015-01-01

This work is focused on the removal of sulphide from wastewater using a two chamber microbial fuel cell, seeded with activated sludge and operated in semi-continuous mode. Two co-substrates were used in order to provide the system for carbon and nutrient source: actual urban wastewater and synthetic wastewater. Results show that sulphide is efficiency depleted (removals over 94%) and that electricity is efficiently produced (maximum power density is 150 mW m(-2)) meanwhile COD is also oxidised (removals higher than 60%). Sulphur and sulphate are obtained as the final products of the oxidation and final speciation depends on the type of co-substrate used. The start-up of the system is very rapid and production of electricity and polarisation curves do not depend on the co-substrate. Copyright © 2015 Elsevier Ltd. All rights reserved.

Methane Emissions from Landfill: Isotopic Evidence for Low Percentage of Oxidation from Gas Wells, Active and Closed Cells

NASA Astrophysics Data System (ADS)

Lowry, David; Fisher, Rebecca; Zazzeri, Giulia; al-Shalaan, Aalia; France, James; Lanoisellé, Mathias; Nisbet, Euan

2017-04-01

Large landfill sites remain a significant source of methane emissions in developed and developing countries, with a global estimated flux of 29 Tg / yr in the EDGAR 2008 database. This is significantly lower than 20 years ago due to the introduction of gas extraction systems, but active cells still emit significant amounts of methane before the gas is ready for extraction. Historically the methane was either passively oxidized through topsoil layers or flared. Oxidation is still the primary method of methane removal in many countries, and covered, remediated cells across the world continue to emit small quantities of methane. The isotopic signatures of methane from landfill gas wells, and that emitted from active and closed cells have been characterized for more than 20 UK landfills since 2011, with more recent work in Kuwait and Hong Kong. Since 2013 the emission plumes have been identified by a mobile measurement system (Zazzeri et al., 2015). Emissions in all 3 countries have a characteristic δ13C signature of -58 ± 3 ‰ dominated by emissions from the active cells, despite the hot, dry conditions of Kuwait and the hot, humid conditions of Hong Kong. Gas well samples define a similar range. Surface emissions from closed cells and closed landfills are mostly in the range -56 to -52 ‰Ṫhese are much more depleted values than those observed in the 1990s (up to -35 ) when soil oxidation was the dominant mechanism of methane removal. Calculations using isotopic signatures of the amount of methane oxidised in these closed areas before emission to atmosphere range from 5 to 15%, but average less than 10%, and are too small to calculate from the high-emitting active cells. Compared to other major methane sources, landfills have the most consistent isotopic signature globally, and are distinct from the more 13C-enriched natural gas, combustion and biomass burning sources. Zazzeri, G. et al. (2015) Plume mapping and isotopic characterization of anthropogenic methane sources, Atmospheric Environment, 110, 151-162, doi.org/10.1016/j.atmosenv.2015.03.029.

A complementary set of electrochemical and X-ray synchrotron techniques to determine the passivation mechanism of iron treated in a new corrosion inhibitor solution specifically developed for the preservation of metallic artefacts

NASA Astrophysics Data System (ADS)

Mirambet, F.; Reguer, S.; Rocca, E.; Hollner, S.; Testemale, D.

2010-05-01

Metallic artefacts of the cultural heritage are often stored in uncontrolled environmental conditions. They are very sensitive to atmospheric corrosion caused by a succession of wet and dry periods due to variations of relative humidity and temperature. To avoid the complete degradation of the metallic artefacts, new preventive strategies must be developed. In this context, we have studied new compounds based on sodium carboxylates solutions CH3(CH2) n-2COO-, Na+ hereafter called NaC n . They allow the formation of a passive layer at the metallic surface composed of a metal-carboxylate complex. To understand the action of those inhibitors in the passivation process of iron we have performed electrochemical measurements and surface characterisation. Moreover, to monitor in real time the growth of the coating, in situ X-ray absorption spectroscopy (XAS) experiments at iron K-edge were carried out in an electrochemical cell. These analyses have shown that in the case of NaC10 solution, the protection of iron surface is correlated to the precipitation of a well-organised layer of FeC10. These experiments confirmed that this compound is a fully oxidised trinuclear Fe(III) complex containing decanoate anions as ligands. Such information concerning the passive layer is a key factor to evaluate its stability and finally the long-term efficiency of the protection treatment.

Analytical high resolution microscopic investigation of organic coating on co-composted biochar

NASA Astrophysics Data System (ADS)

Albu, Mihaela; Mayrhofer, Claudia; Hagemann, Nikolas; Joseph, Stephen; Hofer, Ferdinand; Kothleitner, Gerald

2017-04-01

Aged and/or co-composted biochar amendment improves soil fertility by changing certain proprieties like the porosity and sorption capacity, the redox properties, water holding capacity and nutrient transformations in soil. The beneficial properties have been correlated with surface functional groups resulting from the interactions between black carbon particles, inorganic and organic matter in the soil and soil biota, manure or other compost feedstock. As a result, porous organic layer and organo-mineral phases on the biochar surfaces are formed. This paper presents a detailed analysis of the porous layer and organo-mineral phases formed on co-composted biochar by using high resolution scanning transmission electron microscopy (STEM) and electron energy loss (EELS) as well as energy dispersive X-ray spectroscopy (EDX). The fine structure fingerprints of carbon and nitrogen edges have been used to identify the functional groups, while EDX was used to identify the mineral phases. However, in order to achieve undoubtable results a novel preparation technic of the sample has been developed. The preparation involved 3D gold sputtering on the black carbon particles in order to preserve the surface intact, embedding in resin and, ultrathin microtome cutting. The investigation was carried out using a probe corrected Titan 3G, at a voltage of 60 kV and in cryo-condition, with an EELS energy resolution of 0.15 eV and a spatial resolution down to atomic layers. We proved the presence of both C and N functional groups in the porous, heterogeneous and hydrophilic organic layer and organo-mineral agglomerates. The organic layer fully covered the outer surface of the black carbon piece, but also the surface of internal pores. Its thickness varied from 500-1000 nm on the outer surface down to a couple of nanometres on internal pores. The observed C functional groups have been identified to correspond to: aromatic, aromatic with side chain, ketone, aliphatic, carboxyl/amine carbon and, carbonyl while the N functional groups were: pyridine, imine, amide/peptide, pyrrole, and NO2-/oxidised N. The STEM analysis also revealed the formation of complex organo-mineral agglomerates involving Ca but also the redox-active Fe as iron oxide nnanoparticles and P as magnesium phosphate nnanoparticles. These findings are valuable information which contributes to the understanding of biochar reactions with soil and plants as a function of agronomic practice and environmental factors. Acknowledgment This research received funding from the European Union Seventh Framework Programme under Grant Agreement 312483 - ESTEEM2 (Integrated Infrastructure Initiative-I3).

Oxidative leaching process with cupric ion in hydrochloric acid media for recovery of Pd and Rh from spent catalytic converters.

PubMed

Nogueira, C A; Paiva, A P; Oliveira, P C; Costa, M C; da Costa, A M Rosa

2014-08-15

The recycling of platinum-group metals from wastes such as autocatalytic converters is getting growing attention due to the scarcity of these precious metals and the market pressure originated by increase of demand in current and emerging applications. Hydrometallurgical treatment of such wastes is an alternative way to the most usual pyrometallurgical processes based on smelter operations. This paper focuses on the development of a leaching process using cupric chloride as oxidising agent, in HCl media, for recovery of palladium and rhodium from a spent catalyst. The chloride media allows the adequate conditions for oxidising and solubilising the metals, as demonstrated by equilibrium calculations based on thermodynamic data. The experimental study of the leaching process revealed that Pd solubilisation is clearly easier than that of Rh. The factors temperature, time, and HCl and Cu(2+) concentrations were significant regarding Pd and Rh leaching, the latter requiring higher factor values to achieve the same results. Leaching yields of 95% Pd and 86% Rh were achieved under optimised conditions (T = 80 °C, t = 4h, [HCl] = 6M, [Cu(2+)] = 0.3M). Copyright © 2014 Elsevier B.V. All rights reserved.

Generation of acid mine drainage around the Karaerik copper mine (Espiye, Giresun, NE Turkey): implications from the bacterial population in the Acısu effluent.

PubMed

Sağlam, Emine Selva; Akçay, Miğraç; Çolak, Dilşat Nigar; İnan Bektaş, Kadriye; Beldüz, Ali Osman

2016-09-01

The Karaerik Cu mine is a worked-out deposit with large volumes of tailings and slags which were left around the mine site without any protection. Natural feeding of these material and run-off water from the mineralised zones into the Acısu effluent causes a serious environmental degradation and creation of acid mine drainage (AMD) along its entire length. This research aims at modelling the formation of AMD with a specific attempt on the characterisation of the bacterial population in association with AMD and their role on its occurrence. Based on 16SrRNA analyses of the clones obtained from a composite water sample, the bacterial community was determined to consist of Acidithiobacillus ferrivorans, Ferrovum myxofaciens, Leptospirillum ferrooxidans and Acidithiobacillus ferrooxidans as iron-oxidising bacteria, Acidocella facilis, Acidocella aluminiidurans, Acidiphilium cryptum and Acidiphilium multivorum as iron-reducing bacteria, and Acidithiobacillus ferrivorans, Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and Acidiphilium cryptum as sulphur-oxidising bacteria. This association of bacteria with varying roles was interpreted as evidence of a concomitant occurrence of sulphur and iron cycles during the generation of AMD along the Acısu effluent draining the Karaerik mine.

Microaerobic desulphurisation unit: a new biological system for the removal of H₂S from biogas.

PubMed

Ramos, I; Pérez, R; Fdz-Polanco, M

2013-08-01

A new biotechnology for the removal of H2S from biogas was devised. The desulphurisation conditions present in microaerobic digesters were reproduced inside an external chamber called a microaerobic desulphurisation unit (MDU). A 10 L-unit was inoculated with 1L of digested sludge in order to treat the biogas produced in a pilot digester. During the 128 d of research under such conditions, the average removal efficiency was 94%. The MDU proved to be robust against fluctuations in biogas residence time (57-107 min), inlet H2S concentration (0.17-0.39% v/v), O2/H2S supplied ratio (17.3-1.4 v/v), and temperature (20-35°C). Microbiological analysis confirmed the presence of at least three genera of sulphide-oxidising bacteria. Approximately 60% of all the H2S oxidised was recovered from the bottom of the system in the form of large solid S(0) sheets with 98% w/w of purity. Therefore, this system could become a cost-effective alternative to the conventional biotechniques for biogas desulphurisation. Copyright © 2013 Elsevier Ltd. All rights reserved.

Bismuth selenides from St. Andreasberg, Germany: an oxidised five-element style of mineralisation and its relation to post-Variscan vein-type deposits of central Europe

NASA Astrophysics Data System (ADS)

Cabral, Alexandre Raphael; Ließmann, Wilfried; Jian, Wei; Lehmann, Bernd

2017-10-01

Carbonate veinlets at Roter Bär, a former underground mine in the polymetallic St. Andreasberg vein district of the Harz Mountains, Germany, host selenide minerals that are characterised as Bi-Ag-bearing clausthalite (PbSe), tiemannite (HgSe), guanajuatite (Bi2Se3) and a number of selenides of Bi, Zn, Cu, Ag and Pd. An unnamed Bi-Pb-Ag selenide species with some Hg and Cu, ideally Bi4Pb3Ag2Se10, is reported here. Specular hematite is disseminated within the clausthalite, at the marginal zones of which other selenide minerals are located. The occurrence of bohdanowiczite (AgBiSe2) and umangite (Cu3Se2) constrains the formation temperature to ≤120 °C, and the selenide-hematite assemblage (plus barite in the carbonate gangue) identifies highly oxidised conditions. Selenide assemblages of Pb, Bi, Ag, with and without Co and Ni, occur in many parts of the Variscan basement of central Europe (Harz, Erzgebirge, Schwarzwald and Bohemian Massif) and represent a high-oxidation variety of five-element (Ag-As-Bi-Co-Ni) veins.

Microbial community dynamics in Inferno Crater Lake, a thermally fluctuating geothermal spring

PubMed Central

Ward, Laura; Taylor, Michael W; Power, Jean F; Scott, Bradley J; McDonald, Ian R; Stott, Matthew B

2017-01-01

Understanding how microbial communities respond and adjust to ecosystem perturbation is often difficult to interpret due to multiple and often simultaneous variations in observed conditions. In this research, we investigated the microbial community dynamics of Inferno Crater Lake, an acidic geothermal spring in New Zealand with a unique thermal cycle that varies between 30 and 80 °C over a period of 40–60 days. Using a combination of next-generation sequencing, geochemical analysis and quantitative PCR we found that the microbial community composition was predominantly chemolithotrophic and strongly associated with the thermal cycle. At temperatures >65 °C, the microbial community was dominated almost exclusively by sulphur-oxidising archaea (Sulfolobus-like spp.). By contrast, at mesophilic temperatures the community structure was more mixed, comprising both archaea and bacteria but dominated primarily by chemolithotrophic sulphur and hydrogen oxidisers. Multivariate analysis of physicochemical data confirmed that temperature was the only significant variable associated with community turnover. This research contributes to our understanding of microbial community dynamics in variable environments, using a naturally alternating system as a model and extends our limited knowledge of acidophile ecology in geothermal habitats. PMID:28072418

Microbial community dynamics in Inferno Crater Lake, a thermally fluctuating geothermal spring.

PubMed

Ward, Laura; Taylor, Michael W; Power, Jean F; Scott, Bradley J; McDonald, Ian R; Stott, Matthew B

2017-05-01

Understanding how microbial communities respond and adjust to ecosystem perturbation is often difficult to interpret due to multiple and often simultaneous variations in observed conditions. In this research, we investigated the microbial community dynamics of Inferno Crater Lake, an acidic geothermal spring in New Zealand with a unique thermal cycle that varies between 30 and 80 °C over a period of 40-60 days. Using a combination of next-generation sequencing, geochemical analysis and quantitative PCR we found that the microbial community composition was predominantly chemolithotrophic and strongly associated with the thermal cycle. At temperatures >65 °C, the microbial community was dominated almost exclusively by sulphur-oxidising archaea (Sulfolobus-like spp.). By contrast, at mesophilic temperatures the community structure was more mixed, comprising both archaea and bacteria but dominated primarily by chemolithotrophic sulphur and hydrogen oxidisers. Multivariate analysis of physicochemical data confirmed that temperature was the only significant variable associated with community turnover. This research contributes to our understanding of microbial community dynamics in variable environments, using a naturally alternating system as a model and extends our limited knowledge of acidophile ecology in geothermal habitats.

Onion extract (Allium cepa L.), quercetin and catechin up-regulate paraoxonase 1 activity with concomitant protection against low-density lipoprotein oxidation in male Wistar rats subjected to oxidative stress.

PubMed

Jaiswal, Nidhi; Rizvi, Syed Ibrahim

2014-10-01

Paraoxonase 1 (PON1) protects the oxidative modification of low-density lipoprotein (LDL) and is a major anti-atherosclerotic protein component of high-density lipoprotein. We explored the effect of onion extract and flavonoids (quercetin and catechin) in the regulation of PON1 expression and correlating with oxidised LDL levels in male Wistar rats subjected to mercuric chloride (HgCl₂) induced oxidative insult. Rats were divided into eight groups: Control, Experimental (HgCl₂), Experimental + onion/catechin/quercetin, Positive control (Normal + onion/catechin/quercetin). Treatment continued for 4 weeks. PON1 activity and radical scavenging activity decreased in the Experimental group (P < 0.001) with increased susceptibility of LDL for oxidation and plasma malondialdehyde levels (P < 0.001). Onion extract significantly attenuated the adverse effects of HgCl₂ by up-regulating PON1 activity (P < 0.05), radical scavenging activity (P < 0.01), and protected against LDL oxidation (P < 0.001) and lipid peroxidation (P < 0.01). Similar effects were observed with quercetin and to a lesser extent with catechin. The findings may explain the anti-atherosclerotic effect of onion and also foods containing quercetin and catechins.

The oxidation of alkylaryl sulfides and benzo[b]thiophenes by Escherichia coli cells expressing wild-type and engineered styrene monooxygenase from Pseudomonas putida CA-3.

PubMed

Nikodinovic-Runic, Jasmina; Coulombel, Lydie; Francuski, Djordje; Sharma, Narain D; Boyd, Derek R; Ferrall, Rory Moore O; O'Connor, Kevin E

2013-06-01

Nine different sulfur-containing compounds were biotransformed to the corresponding sulfoxides by Escherichia coli Bl21(DE3) cells expressing styrene monooxygenase (SMO) from Pseudomonas putida CA-3. Thioanisole was consumed at 83.3 μmoles min(-1) g cell dry weight(-1) resulting mainly in the formation of R-thioanisole sulfoxide with an enantiomeric excess (ee) value of 45 %. The rate of 2-methyl-, 2-chloro- and 2-bromo-thioanisole consumption was 2-fold lower than that of thioanisole. Surprisingly, the 2-methylthioanisole sulfoxide product had the opposite (S) configuration to that of the other 2-substituted thioanisole derivatives and had a higher ee value (84 %). The rate of oxidation of 4-substituted thioanisoles was higher than the corresponding 2-substituted substrates but the ee values of the products were consistently lower (10-23 %). The rate of benzo[b]thiophene and 2-methylbenzo[b]thiophene sulfoxidation was approximately 10-fold lower than that of thioanisole. The ee value of the benzo[b]thiophene sulfoxide could not be determined as the product racemized rapidly. E. coli cells expressing an engineered SMO (SMOeng R3-11) oxidised 2-substituted thioanisoles between 1.8- and 2.8-fold faster compared to cells expressing the wild-type enzyme. SMOeng R3-11 oxidised benzo[b]thiophene and 2-methylbenzo[b]thiophene 10.1 and 5.6 times faster that the wild-type enzyme. The stereospecificity of the reaction catalysed by SMOeng was unchanged from that of the wild type. Using the X-ray crystal structure of the P. putida S12 SMO, it was evident that the entrance of substrates into the SMO active site is limited by the binding pocket bottleneck formed by the side chains of Val-211 and Asn-46 carboxyamide group.

Dietary oxidised frying oil causes oxidative damage of pancreatic islets and impairment of insulin secretion, effects associated with vitamin E deficiency.

PubMed

Chiang, Ya-Fan; Shaw, Huey-Mei; Yang, Mei-Fang; Huang, Chih-Yang; Hsieh, Cheng-Hsien; Chao, Pei-Min

2011-05-01

We previously reported that, in rodents, a diet with a high oxidised frying oil (OFO) content leads to glucose intolerance associated with a reduction in insulin secretion. The present study aimed at investigating the impairment of pancreatic islets caused by dietary OFO. C57BL/6J mice were divided into three groups to receive a low-fat basal diet containing 5 g/100 g of fresh soyabean oil (LF group) or a high-fat diet containing 20 g/100 g of either fresh soyabean oil (HF group) or OFO (HO group). After 8 weeks, mice in the HO group showed glucose intolerance and hypoinsulinaemia, and their islets showed impaired glucose-stimulated insulin secretion (P < 0·05; HO group v. LF and HF groups). Significantly higher oxidative stress and a lower mitochondrial membrane potential were observed in the islets in the HO group compared with the LF and HF groups. Immunoblots showed that the reduction in insulin levels in HO islets was associated with activation of the c-Jun NH2-terminal kinase and a reduction in levels of pancreatic and duodenal homeobox factor-1. In a second study, when dietary OFO-induced tissue vitamin E depletion was prevented by large-dose vitamin E supplementation (500 IU(1·06 mmol all-rac-α-tocopherol acetate)/kg diet; HO+E group), the OFO-mediated reduction in islet size and impairment of glucose tolerance and insulin secretion were significantly attenuated (P < 0·05; HO group v. HO+E group). We conclude that a high level of dietary OFO ingestion impairs glucose metabolism by causing oxidative damage and compromising insulin secretion in pancreatic islets, and that these effects can be prevented by vitamin E supplementation.

New natural product -an efficient antimicrobial applications of new newly synthesized pyrimidine derivatives by the electrochemical oxidation of hydroxyl phenol in the presence of 2-mercapto-6-(trifluoromethyl) pyrimidine-4-ol as nucleophile.

PubMed

Khan, Zia Ul Haq; Khan, Amjad; Wan, Pingyu; Khan, Arif Ullah; Tahir, Kamran; Muhammad, Nawshad; Khan, Faheem Ullah; Shah, Hidayat Ullah; Khan, Zia Ullah

2018-05-01

Some new pyrimidine derivatives have been synthesised by electrochemical oxidation of catechol (1a) in the existence of 2-mercapto-6-(trifluoromethyl) pyrimidine-4-ol (3) as a nucleophile in aqueous solution using Cyclic Voltammetric and Controlled Potential Coulometry. The catechol has been oxidised to o-quinone through electrochemical method and participative in Michael addition reaction, leading to the development of some new pyrimidine derivatives. The products were achieved in good yield with high pureness. The mechanism of the reaction has been conformed from the Cyclic Voltammetric data and Controlled Potential Coulometry. After purification, the compounds were characterised using modern techniques. The synthesised materials were screened for antimicrobial actions using Gram positive and Gram negative strain of bacteria. These new synthesised pyrimidine derivatives showed very good antimicrobial activity.

Macrophage Migration Inhibitory Factor is subjected to glucose modification and oxidation in Alzheimer’s Disease

PubMed Central

Kassaar, Omar; Pereira Morais, Marta; Xu, Suying; Adam, Emily L.; Chamberlain, Rosemary C.; Jenkins, Bryony; James, Tony; Francis, Paul T.; Ward, Stephen; Williams, Robert J.; van den Elsen, Jean

2017-01-01

Glucose and glucose metabolites are able to adversely modify proteins through a non-enzymatic reaction called glycation, which is associated with the pathology of Alzheimer’s Disease (AD) and is a characteristic of the hyperglycaemia induced by diabetes. However, the precise protein glycation profile that characterises AD is poorly defined and the molecular link between hyperglycaemia and AD is unknown. In this study, we define an early glycation profile of human brain using fluorescent phenylboronate gel electrophoresis and identify early glycation and oxidation of macrophage migration inhibitory factor (MIF) in AD brain. This modification inhibits MIF enzyme activity and ability to stimulate glial cells. MIF is involved in immune response and insulin regulation, hyperglycaemia, oxidative stress and glycation are all implicated in AD. Our study indicates that glucose modified and oxidised MIF could be a molecular link between hyperglycaemia and the dysregulation of the innate immune system in AD. PMID:28230058

Recent progress in the development of carbonate-intercalated Zn/Cr LDH as a novel photocatalyst for hydrogen evolution aimed at the utilization of solar light.

PubMed

Parida, Kulamani; Mohapatra, Lagnamayee

2012-01-28

A series of novel photocatalysts Zn/Cr LDH with different Zn/Cr molar ratios (2 : 1, 3 : 1, 4 : 1 and 2 : 1-CO(3)) were fabricated by a co-precipitation method and evaluated for photodecomposition of water using visible light irradiation. Various characterization methods were employed to investigate the structures, morphologies and photocatalytic properties. In comparison to Zn/Cr (2 : 1) LDH, Zn/Cr-CO(3) (2 : 1) LDH extends the absorption edges to the visible region and exhibits good photocatalytic activity, even without the assistance of co-catalysts. The visible light photocatalytic activity is ascribed to the charge transfer spectra of octahedral Cr ions in LDH. Zn/Cr-CO(3) LDH shows enhanced photocatalytic activities compared to Zn/Cr LDH as carbonate ions oxidise by holes to form carbonate radicals, inhibit the rapid recombination of e(-) and h(+) charge carriers and thereby suppress the backward reaction to some extent. This work provides a detailed understanding of the semiconductor properties of LDHs for photocatalytical hydrogen evolution.

Ripening and storage conditions of Chétoui and Arbequina olives: Part II. Effect on olive endogenous enzymes and virgin olive oil secoiridoid profile determined by high resolution mass spectrometry.

PubMed

Hachicha Hbaieb, Rim; Kotti, Faten; Cortes-Francisco, Nuria; Caixach, Josep; Gargouri, Mohamed; Vichi, Stefania

2016-11-01

Several factors affect virgin olive oil (VOO) phenolic profile. The aim of this study was to monitor olive hydrolytic (β-glucosidase) and oxidative (peroxydase, POX, and polyphenoloxydase, PPO) enzymes during olive ripening and storage and to determine their capacity to shape VOO phenolic profile. To this end, olives from the cultivars Chétoui and Arbequina were stored at 4°C or 25°C for 4weeks and their enzymatic activities and oil phenolic profiles were compared to those of ripening olives. We observed different trends in enzymes activities according to cultivar and storage temperature. Secoiridoid compounds, determined by high resolution mass spectrometry (HRMS), and their deacetoxylated, oxygenated, and deacetoxy-oxygenated derivatives were identified and their contents differed between the cultivars according to olive ripening degree and storage conditions. These differences could be due to β-glucosidase, POX and PPO activities changes during olive ripening and storage. Results also show that oxidised phenolic compounds could be a marker of VOO ''freshness". Copyright © 2016 Elsevier Ltd. All rights reserved.

Optimisation of the expression of a Trametes versicolor laccase gene in Pichia pastoris.

PubMed

O'Callaghan, J; O'Brien, M M; McClean, K; Dobson, A D W

2002-08-01

A cDNA encoding a laccase enzyme was isolated from a Trametes versicolor cDNA library. The gene was subcloned into the Pichia pastoris expression vector pPIC3.5 and transformed into the P. pastoris strains KM71 and GS115. Laccase-secreting transformants were selected by their ability to oxidise the substrate ABTS. No difference in laccase activity was observed between culture supernatants from GS115 (proteolytic) and KM71 (nonproteolytic) strains. The presence of at least 200 microM copper was necessary for optimal laccase activity in the culture supernatants. During growth of P. pastoris on minimal medium the pH of the medium was reduced to <3.0. If alanine was added to the medium the pH reduction was not as pronounced and at alanine concentrations >0.6% w/v the pH was kept constant for >7 days. Cultures in which the pH was maintained by alanine metabolism produced higher levels of laccase activity than those grown in the absence of alanine. This study describes the development of a medium that allows convenient pH control of P. pastoris without the need for continuous neutralisation.

Oxidation behaviour of zirconium alloys and their precipitates - A mechanistic study

NASA Astrophysics Data System (ADS)

Proff, C.; Abolhassani, S.; Lemaignan, C.

2013-01-01

The precipitate oxidation behaviour of binary zirconium alloys containing 1 wt.% Fe, Ni, Cr or 0.6 wt.% Nb was characterised in TEM on FIB prepared transverse sections of the oxide and reported in previous studies [1,2]. In the present study the following alloys: Zr1%Cu, Zr0.5%Cu0.5%Mo and pure Zr are analysed to add to the available information. In all cases, the observed precipitate oxidation behaviour in the oxide close to the metal-oxide interface could be described either with delayed oxidation with respect to the matrix or simultaneous oxidation as the surrounding zirconium matrix. Attempt was made to explain these observations, with different parameters such as precipitate size and structure, composition and thermodynamic properties. It was concluded that the thermodynamics with the new approach presented could explain most precisely their behaviour, considering the precipitate stoichiometry and the free energy of oxidation of the constituting elements. The surface topography of the oxidised materials, as well as the microstructure of the oxide presenting microcracks have been examined. A systematic presence of microcracks above the precipitates exhibiting delayed oxidation has been found; the height of these crack calculated using the Pilling-Bedworth ratios of different phases present, can explain their origin. The protrusions at the surface in the case of materials containing large precipitates can be unambiguously correlated to the presence of these latter, and the height can be correlated to the Pilling-Bedworth ratios of the phases present as well as the diffusion of the alloying elements to the surface and their subsequent oxidation. This latter behaviour was much more considerable in the case of Fe and Cu with Fe showing systematically diffusion to the outer surface.

Mössbauer Spectra of Clays and Ceramics

NASA Astrophysics Data System (ADS)

Wagner, F. E.; Wagner, U.

2004-06-01

The physical, chemical and mineralogical aspects of the use of Mössbauer spectroscopy in studies of clay-based ceramics are described. Mössbauer spectra of pottery clays fired under oxidising, reducing and changing conditions are explained, and the possibilities of using Mössbauer spectra to derive information on the firing temperatures and the kiln atmosphere during firing in antiquity are discussed and illustrated by examples.

Boiler burden reduced at Bedford site.

PubMed

Horsley, Chris

2011-10-01

With the NHS aiming to reduce its 2007 carbon footprint by 10% by 2015, Chris Horsley, managing director of Babcock Wanson UK, a provider of industrial boilers and burners, thermal oxidisers, air treatment, water treatment, and associated services, looks at how one NHS Trust has approached the challenge, and considerably reduced its carbon emissions, by refurbishing its boiler house and moving from oil to gas-fired steam generation.

Simulation and measurement of complete dye sensitised solar cells: including the influence of trapping, electrolyte, oxidised dyes and light intensity on steady state and transient device behaviour.

PubMed

Barnes, Piers R F; Anderson, Assaf Y; Durrant, James R; O'Regan, Brian C

2011-04-07

A numerical model of the dye sensitised solar cell (DSSC) is used to assess the importance of different loss pathways under various operational conditions. Based on our current understanding, the simulation describes the processes of injection, regeneration, recombination and transport of electrons, oxidised dye molecules and electrolyte within complete devices to give both time dependent and independent descriptions of performance. The results indicate that the flux of electrons lost from the nanocrystalline TiO(2) film is typically at least twice as large under conditions equivalent to 1 sun relative to dark conditions at matched TiO(2) charge concentration. This is in agreement with experimental observations (Barnes et al. Phys. Chem. Chem. Phys. [DOI: 10.1039/c0cp01855d]). The simulated difference in recombination flux is shown to be due to variation in the concentration profile of electron accepting species in the TiO(2) pores between light and dark conditions and to recombination to oxidised dyes in the light. The model is able to easily incorporate non-ideal behaviour of a cell such as the variation of open circuit potential with light intensity and non-first order recombination of conduction band electrons. The time dependent simulations, described by the multiple trapping model of electron transport and recombination, show good agreement with both small and large transient photocurrent and photovoltage measurements at open circuit, including photovoltage rise measurements. The simulation of photovoltage rise also suggests the possibility of assessing the interfacial resistance between the TiO(2) and substrate. When cells with a short diffusion length relative to film thickness were modelled, the simulated small perturbation photocurrent transients at short circuit (but not open circuit) yielded significantly higher effective diffusion coefficients than expected from the mean concentration of electrons and the electrolyte in the cell. This implies that transient measurements can overestimate the electron diffusion length in cells which have a low collection efficiency. The model should provide a useful general framework for exploring new cell descriptions, architectures and other factors influencing device performance.

Genome Analysis of the Biotechnologically Relevant Acidophilic Iron Oxidising Strain JA12 Indicates Phylogenetic and Metabolic Diversity within the Novel Genus “Ferrovum”

PubMed Central

Ullrich, Sophie R.; Poehlein, Anja; Tischler, Judith S.; González, Carolina; Ossandon, Francisco J.; Daniel, Rolf; Holmes, David S.; Schlömann, Michael; Mühling, Martin

2016-01-01

Background Members of the genus “Ferrovum” are ubiquitously distributed in acid mine drainage (AMD) waters which are characterised by their high metal and sulfate loads. So far isolation and microbiological characterisation have only been successful for the designated type strain “Ferrovum myxofaciens” P3G. Thus, knowledge about physiological characteristics and the phylogeny of the genus “Ferrovum” is extremely scarce. Objective In order to access the wider genetic pool of the genus “Ferrovum” we sequenced the genome of a “Ferrovum”-containing mixed culture and successfully assembled the almost complete genome sequence of the novel “Ferrovum” strain JA12. Phylogeny and Lifestyle The genome-based phylogenetic analysis indicates that strain JA12 and the type strain represent two distinct “Ferrovum” species. “Ferrovum” strain JA12 is characterised by an unusually small genome in comparison to the type strain and other iron oxidising bacteria. The prediction of nutrient assimilation pathways suggests that “Ferrovum” strain JA12 maintains a chemolithoautotrophic lifestyle utilising carbon dioxide and bicarbonate, ammonium and urea, sulfate, phosphate and ferrous iron as carbon, nitrogen, sulfur, phosphorous and energy sources, respectively. Unique Metabolic Features The potential utilisation of urea by “Ferrovum” strain JA12 is moreover remarkable since it may furthermore represent a strategy among extreme acidophiles to cope with the acidic environment. Unlike other acidophilic chemolithoautotrophs “Ferrovum” strain JA12 exhibits a complete tricarboxylic acid cycle, a metabolic feature shared with the closer related neutrophilic iron oxidisers among the Betaproteobacteria including Sideroxydans lithotrophicus and Thiobacillus denitrificans. Furthermore, the absence of characteristic redox proteins involved in iron oxidation in the well-studied acidophiles Acidithiobacillus ferrooxidans (rusticyanin) and Acidithiobacillus ferrivorans (iron oxidase) indicates the existence of a modified pathway in “Ferrovum” strain JA12. Therefore, the results of the present study extend our understanding of the genus “Ferrovum” and provide a comprehensive framework for future comparative genome and metagenome studies. PMID:26808278

The effect of amylose content and level of oxidation on the structural changes of acetylated corn starch and generation of free radicals.

PubMed

Pietrzyk, Sławomir; Fortuna, Teresa; Łabanowska, Maria; Juszczak, Lesław; Gałkowska, Dorota; Bączkowicz, Małgorzata; Kurdziel, Magdalena

2018-02-01

This study was aimed at determining the effect of starch oxidation on its acetylation, structure of starch granules, and generation of free radicals. Corn and waxy corn starches were oxidised by NaClO applied in doses of 10, 20, and 30g Cl/kg of starch, and then acetylated using acetic acid anhydride. The carboxyl, carbonyl, acetyl groups were determined in modified starches. Structural properties of starch granules were evaluated based on molecular weight distribution, gelatinisation, crystallinity, specific surface, intrinsic viscosity. EPR measurements were carried out to establish starch susceptibility to UV irradiation induced generation of free radicals. It was found that the number of carbon centered radicals was dependent on the kind of starch and its chemical modification. Study results allowed concluding that the applied modifications contributed to significant changes in starch granules that were determined not only by the amylose content of starch but also by the degree of its oxidation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Silver and copper nanoclusters in the lustre decoration of Italian Renaissance pottery: an EXAFS study

NASA Astrophysics Data System (ADS)

Padovani, S.; Borgia, I.; Brunetti, B.; Sgamellotti, A.; Giulivi, A.; D'Acapito, F.; Mazzoldi, P.; Sada, C.; Battaglin, G.

Lustre is one of the most important decorative techniques of the Medieval and Renaissance pottery of the Mediterranean basin, capable of producing brilliant metallic reflections and iridescence. Following the recent finding that the colour of lustre decorations is mainly determined by copper and silver nanoclusters dispersed in the glaze layer, the local environment of copper and silver atoms has been studied by extended X-ray absorption fine structure (EXAFS) spectroscopy on original samples of gold and red lustre. It has been found that, in gold lustre, whose colour is attributed mainly to the silver nanocluster dispersion, silver is only partially present in the metallic form and copper is almost completely oxidised. In the red lustre, whose colour is attributed mainly to the copper nanocluster dispersion, only a fraction of copper is present in the metallic form. EXAFS measurements on red lustre, carried out in the total electron yield mode to probe only the first 150 nm of the glaze layer, indicated that in some cases lustre nanoclusters may be confined in a very thin layer close to the surface.

Highly oxidising fluids generated during serpentinite breakdown in subduction zones.

PubMed

Debret, B; Sverjensky, D A

2017-09-04

Subduction zones facilitate chemical exchanges between Earth's deep interior and volcanism that affects habitability of the surface environment. Lavas erupted at subduction zones are oxidized and release volatile species. These features may reflect a modification of the oxidation state of the sub-arc mantle by hydrous, oxidizing sulfate and/or carbonate-bearing fluids derived from subducting slabs. But the reason that the fluids are oxidizing has been unclear. Here we use theoretical chemical mass transfer calculations to predict the redox state of fluids generated during serpentinite dehydration. Specifically, the breakdown of antigorite to olivine, enstatite, and chlorite generates fluids with high oxygen fugacities, close to the hematite-magnetite buffer, that can contain significant amounts of sulfate. The migration of these fluids from the slab to the mantle wedge could therefore provide the oxidized source for the genesis of primary arc magmas that release gases to the atmosphere during volcanism. Our results also show that the evolution of oxygen fugacity in serpentinite during subduction is sensitive to the amount of sulfides and potentially metal alloys in bulk rock, possibly producing redox heterogeneities in subducting slabs.

Physiological integration enhanced the tolerance of Cynodon dactylon to flooding.

PubMed

Li, Z J; Fan, D Y; Chen, F Q; Yuan, Q Y; Chow, W S; Xie, Z Q

2015-03-01

Many flooding-tolerant species are clonal plants; however, the effects of physiological integration on plant responses to flooding have received limited attention. We hypothesise that flooding can trigger changes in metabolism of carbohydrates and ROS (reactive oxygen species) in clonal plants, and that physiological integration can ameliorate the adverse effects of stress, subsequently restoring the growth of flooded ramets. In the present study, we conducted a factorial experiment combining flooding to apical ramets and stolon severing (preventing physiological integration) between apical and basal ramets of Cynodon dactylon, which is a stoloniferous perennial grass with considerable flooding tolerance. Flooding-induced responses including decreased root biomass, accumulation of soluble sugar and starch, as well as increased activity of superoxide dismutase (SOD) and ascorbate peroxidase (APX) in apical ramets. Physiological integration relieved growth inhibition, carbohydrate accumulation and induction of antioxidant enzyme activity in stressed ramets, as expected, without any observable cost in unstressed ramets. We speculate that relief of flooding stress in clonal plants may rely on oxidising power and electron acceptors transferred between ramets through physiological integration. © 2014 German Botanical Society and The Royal Botanical Society of the Netherlands.

Betaine:homocysteine methyltransferase--a new assay for the liver enzyme and its absence from human skin fibroblasts and peripheral blood lymphocytes.

PubMed

Wang, J A; Dudman, N P; Lynch, J; Wilcken, D E

1991-12-31

Chronic elevation of plasma homocysteine is associated with increased atherogenesis and thrombosis, and can be lowered by betaine (N,N,N-trimethylglycine) treatment which is thought to stimulate activity of the enzyme betaine:homocysteine methyltransferase. We have developed a new assay for this enzyme, in which the products of the enzyme-catalysed reaction between betaine and homocysteine are oxidised by performic acid before being separated and quantified by amino acid analysis. This assay confirmed that human liver contains abundant betaine:homocysteine methyltransferase (33.4 nmol/h/mg protein at 37 degrees C, pH 7.4). Chicken and lamb livers also contain the enzyme, with respective activities of 50.4 and 6.2 nmol/h/mg protein. However, phytohaemagglutinin-stimulated human peripheral blood lymphocytes and cultured human skin fibroblasts contained no detectable betaine:homocysteine methyltransferase (less than 1.4 nmol/h/mg protein), even after cells were pre-cultured in media designed to stimulate production of the enzyme. The results emphasize the importance of the liver in mediating the lowering of elevated circulating homocysteine by betaine.

Respiratory Health Effects of Volcanic Ash - a new Approach

NASA Astrophysics Data System (ADS)

Horwell, C. J.; Fenoglio, I.; Sparks, R. J.; Ragnarsdottir, K. V.; Fubini, B.

2003-12-01

Attempts to characterise the toxicity of volcanic ash have focused on the presence of the crystalline silica polymorph cristobalite, which is known to cause silicosis and lung cancer in industrial settings. Within the lung, it is the surface of the particles which will react with endogenous molecules. Free radicals, produced on particle surfaces, can react with DNA and other cellular components, instigating a chain of toxic events. For the first time, the ability of volcanic ash to form free radicals has been assessed using Electron Paramagnetic Resonance techniques specific to the hydroxyl radical. Respirable (< 4 microns) crystalline silica, separated from volcanic ash from the Soufriere Hills volcano, Montserrat, West Indies, did not produce hydroxyl free radicals or surface radicals. However, the ash, itself, generated up to 3 times more hydroxyl radicals than a quartz of known toxicity. The cause of the reactivity is reduced iron on the surface of iron-rich minerals such as amphiboles and pyroxenes. Fresh volcanic ash generates more free radicals than weathered volcanic ash which will have oxidised (and leached away) surface iron. These results have implications for volcanic health hazard research as it was previously assumed that volcanoes which did not produce respirable crystalline silica presented a lesser respiratory health hazard. The International Volcanic Health Hazard Network (IVHHN) promotes research into the health effects of volcanic emissions. Under the auspices of IVHHN, volcanic ash samples from volcanoes world-wide are being analysed for surface reactivity, grain-size distribution and composition to form a comprehensive database for use by volcano observatories, emergency managers, medical practitioners and researchers. The results will highlight volcanoes which have the potential to cause a respiratory health hazard through generation of iron-catalysed free radicals, as well as more conventional markers such as concentration of respirable particles. At the onset of new eruptions, the database will be used to aid the rapid assessment of health hazard from volcanic ash.

Impact of chlorinated disinfection on copper corrosion in hot water systems

NASA Astrophysics Data System (ADS)

Montes, J. Castillo; Hamdani, F.; Creus, J.; Touzain, S.; Correc, O.

2014-09-01

In France, hot water quality control inside buildings is occasionally ensured by disinfection treatments using temperature increases or addition of sodium hypochlorite (between 0.5 ppm and 1 ppm residual free chlorine). This disinfectant is a strong oxidiser and it could interact with metallic pipes usually used in hot water systems. This work deals with the study of the impact of these treatments on the durability of copper pipes. The objective of this work was to investigate the influence of sodium hypochlorite concentration and temperature on the copper corrosion mechanism. Copper samples were tested under dynamic and static conditions of ageing with sodium hypochlorite solutions ranging from 0 to 100 ppm with temperature at 50 °C and 70 °C. The efficiency of a corrosion inhibitor was investigated in dynamic conditions. Visual observations and analytical analyses of the internal surface of samples was studied at different ageing duration. Corrosion products were characterised by X-ray diffraction and Raman spectroscopy. Temperature and disinfectant were found to considerably affect the copper corrosion mechanism. Surprisingly, the corrosiveness of the solution was higher at lower temperatures. The temperature influences the nature of corrosion products. The protection efficiency is then strongly depend on the nature of the corrosion products formed at the surface of copper samples exposed to the aggressive solutions containing different concentration of disinfectant.

Metabolic fate of saturated and monounsaturated dietary fats: the Mediterranean diet revisited from epidemiological evidence to cellular mechanisms.

PubMed

Bergouignan, Audrey; Momken, Iman; Schoeller, Dale A; Simon, Chantal; Blanc, Stéphane

2009-01-01

Increasing evidence indicates favourable effects of the Mediterranean diet, partly associated to its monounsaturated fatty acids (MUFA) content on both obesity and diabetes. However, neither the underlying mechanisms by which the Mediterranean diet exerts its protective effect, nor the interplay with other environmental factors (i.e. physical activity), are fully characterised. In this review, we examined recent data on how the metabolic fate of MUFA and saturated fatty acids (SFA) differs. Because of differential packaging into lipoproteins, hydrolysis of triacylglycerol-rich lipoproteins by lipoprotein lipase and transport into oxidative tissues, MUFA are oxidised more than SFA. This high MUFA oxidation favour lipid oxidation and according to the oxidative balance concept reduces the risk of obesity. It also improves the intra-muscular triacylglycerol turnover, which mitigates the SFA-induced accumulation of diacylglycerol and ceramides, and thus protects the insulin sensitivity and cell viability. Finally, physical activity through its action on the energy turnover differentially regulates the metabolism of SFA and MUFA. The putative combined role of AMP-activated kinase and mitochondrial glycerol-3-phosphate transferase on the intra-muscular partitioning of MUFA and SFA provides new areas of research to better understand the beneficial effects of the Mediterranean diet and physical activity on obesity and diabetes.

A modelling assessment of acidification and recovery of European surface waters

NASA Astrophysics Data System (ADS)

Jenkins, A.; Camarero, L.; Cosby, B. J.; Ferrier, R. C.; Forsius, M.; Helliwell, R. C.; Kopácek, J.; Majer, V.; Moldan, F.; Posch, M.; Rogora, M.; Schöpp, W.; Wright, R. F.

The increase in emission of sulphur oxides and nitrogen (both oxidised and reduced forms) since the mid-1800s caused a severe decline in pH and ANC in acid-sensitive surface waters across Europe. Since c.1980, these emissions have declined and trends towards recovery from acidification have been widely observed in time-series of water chemistry data. In this paper, the MAGIC model was applied to 10 regions (the SMART model to one) in Europe to address the question of future recovery under the most recently agreed emission protocols (the 1999 Gothenburg Protocol). The models were calibrated using best available data and driven using S and N deposition sequences for Europe derived from EMEP data. The wide extent and the severity of water acidification in 1980 in many regions were illustrated by model simulations which showed significant deterioration in ANC away from the pre-acidification conditions. The simulations also captured the recovery to 2000 in response to the existing emission reductions. Predictions to 2016 indicated further significant recovery towards pre-acidification chemistry in all regions except Central England (S Pennines), S Alps, S Norway and S Sweden. In these areas it is clear that further emission reductions will be required and that the recovery of surface waters will take several decades as soils slowly replenish their depleted base cation pools. Chemical recovery may not, however, ensure biological recovery and further reductions may also be required to enable these waters to achieve the "good ecological status" as required by the EU Water Framework Directive.

Global modelling of the total OH reactivity: investigations on the "missing" OH sink and its atmospheric implications

NASA Astrophysics Data System (ADS)

Ferracci, Valerio; Heimann, Ines; Abraham, N. Luke; Pyle, John A.; Archibald, Alexander T.

2018-05-01

The hydroxyl radical (OH) plays a crucial role in the chemistry of the atmosphere as it initiates the removal of most trace gases. A number of field campaigns have observed the presence of a missing OH sink in a variety of regions across the planet. A comparison of direct measurements of the OH loss frequency, also known as total OH reactivity (kOH), with the sum of individual known OH sinks (obtained via the simultaneous detection of species such as volatile organic compounds and nitrogen oxides) indicates that, in some cases, up to 80 % of kOH is unaccounted for. In this work, the UM-UKCA chemistry-climate model was used to investigate the wider implications of the missing reactivity on the oxidising capacity of the atmosphere. Simulations of the present-day atmosphere were performed and the model was evaluated against an array of field measurements to verify that the known OH sinks were reproduced well, with a resulting good agreement found for most species. Following this, an additional sink was introduced to simulate the missing OH reactivity as an emission of a hypothetical molecule, X, which undergoes rapid reaction with OH. The magnitude and spatial distribution of this sink were underpinned by observations of the missing reactivity. Model runs showed that the missing reactivity accounted for on average 6 % of the total OH loss flux at the surface and up to 50 % in regions where emissions of the additional sink were high. The lifetime of the hydroxyl radical was reduced by 3 % in the boundary layer, whilst tropospheric methane lifetime increased by 2 % when the additional OH sink was included. As no OH recycling was introduced following the initial oxidation of X, these results can be interpreted as an upper limit of the effects of the missing reactivity on the oxidising capacity of the troposphere. The UM-UKCA simulations also allowed us to establish the atmospheric implications of the newly characterised reactions of peroxy radicals (RO2) with OH. Whilst the effects of this chemistry on kOH were minor, the reaction of the simplest peroxy radical, CH3O2, with OH was found to be a major sink for CH3O2 and source of HO2 over remote regions at the surface and in the free troposphere. Inclusion of this reaction in the model increased tropospheric methane lifetime by up to 3 %, depending on its product branching. Simulations based on the latest kinetic and product information showed that this reaction cannot reconcile models with observations of atmospheric methanol, in contrast to recent suggestions.

Performance Versus Safety of Some Primary and Rechargeable Lithium Batteries

DTIC Science & Technology

2004-12-01

which can ignite during abuse. At the same time, manganese dioxide is an oxidising agent and it decomposes at 535oC, giving off oxygen, thus...is endothermic for nicad but exothermic for nickel- metal hydride. Therefore, nickel-metal hydride cells are more prone to damage from...With nail penetration, Figure 6. Photograph showing damage inflicted onto a lithium-ion gel-polymer cell by several hammer blows

Sequential continuous flow processes for the oxidation of amines and azides by using HOF·MeCN.

PubMed

McPake, Christopher B; Murray, Christopher B; Sandford, Graham

2012-02-13

The generation and use of the highly potent oxidising agent HOF·MeCN in a controlled single continuous flow process is described. Oxidations of amines and azides to corresponding nitrated systems by using fluorine gas, water and acetonitrile by sequential gas-liquid/liquid-liquid continuous flow procedures are reported. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Combustible Cartridge Cases, an Account of the Current Technology and Proposals for Future Development.

DTIC Science & Technology

1986-10-01

mixture of energetic nitrocellulose libres and inert cellulose fibres. Additives, such as polymeric wet strength resins, fillers, waxes and other...produced using inert cellulosic materials, while incorporation of nitrocellulose, a strong oxidiser, results in a ’ombustible’ product. At present...textiles with wet strength resins. The nitrated cellulosic fabric was laminated by winding around a collapsible mandrel which is rotated under pressure

DehydroalanylGly, a new post translational modification resulting from the breakdown of glutathione.

PubMed

Friedrich, Michael G; Wang, Zhen; Schey, Kevin L; Truscott, Roger J W

2018-04-01

The human body contains numerous long-lived proteins which deteriorate with age, typically by racemisation, deamidation, crosslinking and truncation. Previously we elucidated one reaction responsible for age-related crosslinking, the spontaneous formation of dehydroalanine (DHA) intermediates from phosphoserine and cysteine. This resulted in non-disulphide covalent crosslinks. The current paper outlines a novel posttranslational modification (PTM) in human proteins, which involves the addition of dehydroalanylglycine (DHAGly) to Lys residues. Human lens digests were examined by mass spectrometry for the presence of (DHA)Gly (+144.0535 Da) adducts to Lys residues. Peptide model studies were undertaken to elucidate the mechanism of formation. In the lens, this PTM was detected at 18 lysine sites in 7 proteins. Using model peptides, a pathway for its formation was found to involve initial formation of the glutathione degradation product, γ-Glu(DHA)Gly from oxidised glutathione (GSSG). Once the Lys adduct formed, the Glu residue was lost in a hydrolytic mechanism apparently catalysed by the ε-amino group of the Lys. This discovery suggests that within cells, the functional groups of amino acids in proteins may be susceptible to modification by reactive metabolites derived from GSSG. Our finding demonstrates a novel +144.0535 Da PTM arising from the breakdown of oxidised glutathione. Copyright © 2018. Published by Elsevier B.V.

Observation of asphalt binder microstructure with ESEM.

PubMed

Mikhailenko, P; Kadhim, H; Baaj, H; Tighe, S

2017-09-01

The observation of asphalt binder with the environmental scanning electron microscope (ESEM) has shown the potential to observe asphalt binder microstructure and its evolution with binder aging. A procedure for the induction and identification of the microstructure in asphalt binder was established in this study and included sample preparation and observation parameters. A suitable heat-sampling asphalt binder sample preparation method was determined for the test and several stainless steel and Teflon sample moulds developed, finding that stainless steel was the preferable material. The magnification and ESEM settings conducive to observing the 3D microstructure were determined through a number of observations to be 1000×, although other magnifications could be considered. Both straight run binder (PG 58-28) and an air blown oxidised binder were analysed; their structures being compared for their relative size, abundance and other characteristics, showing a clear evolution in the fibril microstructure. The microstructure took longer to appear for the oxidised binder. It was confirmed that the fibril microstructure corresponded to actual characteristics in the asphalt binder. Additionally, a 'bee' micelle structure was found as a transitional structure in ESEM observation. The test methods in this study will be used for more comprehensive analysis of asphalt binder microstructure. © 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society.

Isolation of 'Candidatus Nitrosocosmicus franklandus', a novel ureolytic soil archaeal ammonia oxidiser with tolerance to high ammonia concentration.

PubMed

Lehtovirta-Morley, Laura E; Ross, Jenna; Hink, Linda; Weber, Eva B; Gubry-Rangin, Cécile; Thion, Cécile; Prosser, James I; Nicol, Graeme W

2016-05-01

Studies of the distribution of ammonia oxidising archaea (AOA) and bacteria (AOB) suggest distinct ecological niches characterised by ammonia concentration and pH, arising through differences in substrate affinity and ammonia tolerance. AOA form five distinct phylogenetic clades, one of which, the 'Nitrososphaera sister cluster', has no cultivated isolate. A representative of this cluster, named 'Candidatus Nitrosocosmicus franklandus', was isolated from a pH 7.5 arable soil and we propose a new cluster name:'Nitrosocosmicus' While phylogenetic analysis of amoA genes indicates its association with the Nitrososphaera sister cluster, analysis of 16S rRNA genes provided no support for a relative branching that is consistent with a 'sister cluster', indicating placement within a lineage of the order Nitrososphaerales 'Ca.N. franklandus' is capable of ureolytic growth and its tolerances to nitrite and ammonia are higher than in other AOA and similar to those of typical soil AOB. Similarity of other growth characteristics of 'Ca.N. franklandus' with those of typical soil AOB isolates reduces support for niche differentiation between soil AOA and AOB and suggests that AOA have a wider physiological diversity than previously suspected. In particular, the high ammonia tolerance of 'Ca.N. franklandus' suggests potential contributions to nitrification in fertilised soils. © FEMS 2016.

Evaluating the potential impact of proton carriers on syntrophic propionate oxidation

NASA Astrophysics Data System (ADS)

Juste-Poinapen, Natacha M. S.; Turner, Mark S.; Rabaey, Korneel; Virdis, Bernardino; Batstone, Damien J.

2015-12-01

Anaerobic propionic acid degradation relies on interspecies electron transfer (IET) between propionate oxidisers and electron acceptor microorganisms, via either molecular hydrogen, formate or direct transfers. We evaluated the possibility of stimulating direct IET, hence enhancing propionate oxidation, by increasing availability of proton carriers to decrease solution resistance and reduce pH gradients. Phosphate was used as a proton carrying anion, and chloride as control ion together with potassium as counter ion. Propionic acid consumption in anaerobic granules was assessed in a square factorial design with ratios (1:0, 2:1, 1:1, 1:2 and 0:1) of total phosphate (TP) to Cl-, at 1X, 10X, and 30X native conductivity (1.5 mS.cm-1). Maximum specific uptake rate, half saturation, and time delay were estimated using model-based analysis. Community profiles were analysed by fluorescent in situ hybridisation and 16S rRNA gene pyrosequencing. The strongest performance was at balanced (1:1) ratios at 10X conductivity where presumptive propionate oxidisers namely Syntrophobacter and Candidatus Cloacamonas were more abundant. There was a shift from Methanobacteriales at high phosphate, to Methanosaeta at low TP:Cl ratios and low conductivity. A lack of response to TP, and low percentage of presumptive electroactive organisms suggested that DIET was not favoured under the current experimental conditions.

Omega-3 fatty acids attenuate constitutive and insulin-induced CD36 expression through a suppression of PPAR α/γ activity in microvascular endothelial cells.

PubMed

Madonna, Rosalinda; Salerni, Sara; Schiavone, Deborah; Glatz, Jan F; Geng, Yong-Jian; De Caterina, Raffaele

2011-09-01

Microvascular dysfunction occurs in insulin resistance and/or hyperinsulinaemia. Enhanced uptake of free fatty acids (FFA) and oxidised low-density lipoproteins (oxLDL) may lead to oxidative stress and microvascular dysfunction interacting with CD36, a PPARα/γ-regulated scavenger receptor and long-chain FFA transporter. We investigated CD36 expression and CD36-mediated oxLDL uptake before and after insulin treatment in human dermal microvascular endothelial cells (HMVECs), ± different types of fatty acids (FA), including palmitic, oleic, linoleic, arachidonic, eicosapentaenoic (EPA), and docosahexaenoic (DHA) acids. Insulin (10(-8) and 10(-7) M) time-dependently increased DiI-oxLDL uptake and CD36 surface expression (by 30 ± 13%, p<0.05 vs. untreated control after 24 hours incubation), as assessed by ELISA and flow cytometry, an effect that was potentiated by the PI3-kinase inhibitor wortmannin and reverted by the ERK1/2 inhibitor PD98059 and the PPARα/γ antagonist GW9662. A ≥ 24 hour exposure to 50 μM DHA or EPA, but not other FA, blunted both the constitutive (by 23 ± 3% and 29 ± 2%, respectively, p<0.05 for both) and insulin-induced CD36 expressions (by 45 ± 27 % and 12 ± 3 %, respectively, p<0.05 for both), along with insulin-induced uptake of DiI-oxLDL and the downregulation of phosphorylated endothelial nitric oxide synthase (P-eNOS). At gel shift assays, DHA reverted insulin-induced basal and oxLDL-stimulated transactivation of PPRE and DNA binding of PPARα/γ and NF-κB. In conclusion, omega-3 fatty acids blunt the increased CD36 expression and activity promoted by high concentrations of insulin. Such mechanisms may be the basis for the use of omega-3 fatty acids in diabetic microvasculopathy.

Alkali activation of recovered fuel-biofuel fly ash from fluidised-bed combustion: Stabilisation/solidification of heavy metals.

PubMed

Yliniemi, Juho; Pesonen, Janne; Tiainen, Minna; Illikainen, Mirja

2015-09-01

Recovered fuel-biofuel fly ash from a fluidized bed boiler was alkali-activated and granulated with a sodium-silicate solution in order to immobilise the heavy metals it contains. The effect of blast-furnace slag and metakaolin as co-binders were studied. Leaching standard EN 12457-3 was applied to evaluate the immobilisation potential. The results showed that Ba, Pb and Zn were effectively immobilised. However, there was increased leaching after alkali activation for As, Cu, Mo, Sb and V. The co-binders had minimal or even negative effect on the immobilisation. One exception was found for Cr, in which the slag decreased leaching, and one was found for Cu, in which the slag increased leaching. A sequential leaching procedure was utilized to gain a deeper understanding of the immobilisation mechanism. By using a sequential leaching procedure it is possible fractionate elements into watersoluble, acid-soluble, easily-reduced and oxidisable fractions, yielding a total 'bioavailable' amount that is potentially hazardous for the environment. It was found that the total bioavailable amount was lower following alkali activation for all heavy metals, although the water-soluble fraction was higher for some metals. Evidence from leaching tests suggests the immobilisation mechanism was chemical retention, or trapping inside the alkali activation reaction products, rather than physical retention, adsorption or precipitation as hydroxides. Copyright © 2015 Elsevier Ltd. All rights reserved.

Functionalised zinc oxide nanowire gas sensors: Enhanced NO(2) gas sensor response by chemical modification of nanowire surfaces.

PubMed

Waclawik, Eric R; Chang, Jin; Ponzoni, Andrea; Concina, Isabella; Zappa, Dario; Comini, Elisabetta; Motta, Nunzio; Faglia, Guido; Sberveglieri, Giorgio

2012-01-01

Surface coating with an organic self-assembled monolayer (SAM) can enhance surface reactions or the absorption of specific gases and hence improve the response of a metal oxide (MOx) sensor toward particular target gases in the environment. In this study the effect of an adsorbed organic layer on the dynamic response of zinc oxide nanowire gas sensors was investigated. The effect of ZnO surface functionalisation by two different organic molecules, tris(hydroxymethyl)aminomethane (THMA) and dodecanethiol (DT), was studied. The response towards ammonia, nitrous oxide and nitrogen dioxide was investigated for three sensor configurations, namely pure ZnO nanowires, organic-coated ZnO nanowires and ZnO nanowires covered with a sparse layer of organic-coated ZnO nanoparticles. Exposure of the nanowire sensors to the oxidising gas NO(2) produced a significant and reproducible response. ZnO and THMA-coated ZnO nanowire sensors both readily detected NO(2) down to a concentration in the very low ppm range. Notably, the THMA-coated nanowires consistently displayed a small, enhanced response to NO(2) compared to uncoated ZnO nanowire sensors. At the lower concentration levels tested, ZnO nanowire sensors that were coated with THMA-capped ZnO nanoparticles were found to exhibit the greatest enhanced response. ΔR/R was two times greater than that for the as-prepared ZnO nanowire sensors. It is proposed that the ΔR/R enhancement in this case originates from the changes induced in the depletion-layer width of the ZnO nanoparticles that bridge ZnO nanowires resulting from THMA ligand binding to the surface of the particle coating. The heightened response and selectivity to the NO(2) target are positive results arising from the coating of these ZnO nanowire sensors with organic-SAM-functionalised ZnO nanoparticles.

Studies of the Electrochemical Detection of Thiols. Part 2. An Investigation of the Reactions Occurring in NAIAD, and the Effect of HCN, Guaiacol and GB on these Reactions

DTIC Science & Technology

1977-01-01

OF THE REDUCTION OF CHOLINE T DISULPHIDE (5 x 10-4 M) AT A PLATINUM ELECTRODE UNDER STATIONARY, DEOXYGENATED CONDITIONS Sweep rate Cathodic current... voltametry (10 - 100 s) which reoxidises at E = -0.7V. This product is not thiocholine, which is oxidised at E = +0.8V, and was not 3; identified. Thus, in

Structure, morphology and functionality of acetylated and oxidised barley starches.

PubMed

El Halal, Shanise Lisie Mello; Colussi, Rosana; Pinto, Vânia Zanella; Bartz, Josiane; Radunz, Marjana; Carreño, Neftali Lenin Villarreal; Dias, Alvaro Renato Guerra; Zavareze, Elessandra da Rosa

2015-02-01

Acetylation and oxidation are chemical modifications which alter the properties of starch. The degree of modification of acetylated and oxidized starches is dependent on the catalyst and active chlorine concentrations, respectively. The objective of this study was to evaluate the effect of acetylation and oxidation on the structural, morphological, physical-chemical, thermal and pasting properties of barley starch. Barley starches were acetylated at different catalyst levels (11%, 17%, and 23% of NaOH solution) and oxidized at different sodium hypochlorite concentrations (1.0%, 1.5%, and 2.0% of active chlorine). Fourier-transformed infrared spectroscopy (FTIR), X-ray diffractograms, thermal, morphological, and pasting properties, swelling power and solubility of starches were evaluated. The degree of substitution (DS) of the acetylated starches increased with the rise in catalyst concentration. The percentage of carbonyl (CO) and carboxyl (COOH) groups in oxidized starches also increased with the rise of active chlorine level. The presence of hydrophobic acetyl groups, carbonyl and carboxyl groups caused a partial disorganization and depolymerization of starch granules. The structural, morphological and functional changes in acetylated and oxidized starches varied according to reaction conditions. Acetylation makes barley starch more hydrophobic by the insertion of acetyl groups. Also the oxidation promotes low retrogradation and viscosity. All these characteristics are important for biodegradable film production. Copyright © 2014 Elsevier Ltd. All rights reserved.

Theoretical investigation of aerobic and anaerobic oxidative inactivation of the [NiFe]-hydrogenase active site.

PubMed

Breglia, Raffaella; Greco, Claudio; Fantucci, Piercarlo; De Gioia, Luca; Bruschi, Maurizio

2018-01-17

The extraordinary capability of [NiFe]-hydrogenases to catalyse the reversible interconversion of protons and electrons into dihydrogen (H 2 ) has stimulated numerous experimental and theoretical studies addressing the direct utilization of these enzymes in H 2 production processes. Unfortunately, the introduction of these natural H 2 -catalysts in biotechnological applications is limited by their inhibition under oxidising (aerobic and anaerobic) conditions. With the aim of contributing to overcome this limitation, we studied the oxidative inactivation mechanism of [NiFe]-hydrogenases by performing Density Functional Theory (DFT) calculations on a very large model of their active site in which all the amino acids forming the first and second coordination spheres of the NiFe cluster have been explicitly included. We identified an O 2 molecule and two H 2 O molecules as sources of the two oxygen atoms that are inserted at the active site of the inactive forms of the enzyme (Ni-A and Ni-B) under aerobic and anaerobic conditions, respectively. Furthermore, our results support the experimental evidence that the Ni-A-to-Ni-B ratio strongly depends on the number of reducing equivalents available for the process and on the oxidizing conditions under which the reaction takes place.

Cell oxidation-reduction imbalance after modulated radiofrequency radiation.

PubMed

Marjanovic, Ana Marija; Pavicic, Ivan; Trosic, Ivancica

2015-01-01

Aim of this study was to evaluate an influence of modulated radiofrequency field (RF) of 1800 MHz, strength of 30 V/m on oxidation-reduction processes within the cell. The assigned RF field was generated within Gigahertz Transversal Electromagnetic Mode cell equipped by signal generator, modulator, and amplifier. Cell line V79, was irradiated for 10, 30, and 60 min, specific absorption rate was calculated to be 1.6 W/kg. Cell metabolic activity and viability was determined by MTT assay. In order to define total protein content, colorimetric method was used. Concentration of oxidised proteins was evaluated by enzyme-linked immunosorbent assay. Reactive oxygen species (ROS) marked with fluorescent probe 2',7'-dichlorofluorescin diacetate were measured by means of plate reader device. In comparison with control cell samples, metabolic activity and total protein content in exposed cells did not differ significantly. Concentrations of carbonyl derivates, a product of protein oxidation, insignificantly but continuously increase with duration of exposure. In exposed samples, ROS level significantly (p < 0.05) increased after 10 min of exposure. Decrease in ROS level was observed after 30-min treatment indicating antioxidant defence mechanism activation. In conclusion, under the given laboratory conditions, modulated RF radiation might cause impairment in cell oxidation-reduction equilibrium within the growing cells.

High-rate, High Temperature Acetotrophic Methanogenesis Governed by a Three Population Consortium in Anaerobic Bioreactors

PubMed Central

Ho, Dang; Jensen, Paul; Gutierrez-Zamora, Maria-Luisa; Beckmann, Sabrina; Manefield, Mike; Batstone, Damien

2016-01-01

A combination of acetate oxidation and acetoclastic methanogenesis has been previously identified to enable high-rate methanogenesis at high temperatures (55 to 65°C), but this capability had not been linked to any key organisms. This study combined RNA–stable isotope probing on 13C-labelled acetate and 16S amplicon sequencing to identify the active micro-organisms involved in high-rate methanogenesis. Active biomass was harvested from three bench-scale thermophilic bioreactors treating waste activated sludge at 55, 60 and 65°C, and fed with 13-C labelled and 12C-unlabelled acetate. Acetate uptake and cumulative methane production were determined and kinetic parameters were estimated using model-based analysis. Pyrosequencing performed on 13C- enriched samples indicated that organisms accumulating labelled carbon were Coprothermobacter (all temperatures between 55 and 65°C), acetoclastic Methanosarcina (55 to 60°C) and hydrogenotrophic Methanothermobacter (60 to 65°C). The increased relative abundance of Coprothermobacter with increased temperature corresponding with a shift to syntrophic acetate oxidation identified this as a potentially key oxidiser. Methanosarcina likely acts as both a hydrogen utilising and acetoclastic methanogen at 55°C, and is replaced by Methanothermobacter as a hydrogen utiliser at higher temperatures. PMID:27490246

High-rate, High Temperature Acetotrophic Methanogenesis Governed by a Three Population Consortium in Anaerobic Bioreactors.

PubMed

Ho, Dang; Jensen, Paul; Gutierrez-Zamora, Maria-Luisa; Beckmann, Sabrina; Manefield, Mike; Batstone, Damien

2016-01-01

A combination of acetate oxidation and acetoclastic methanogenesis has been previously identified to enable high-rate methanogenesis at high temperatures (55 to 65°C), but this capability had not been linked to any key organisms. This study combined RNA-stable isotope probing on 13C-labelled acetate and 16S amplicon sequencing to identify the active micro-organisms involved in high-rate methanogenesis. Active biomass was harvested from three bench-scale thermophilic bioreactors treating waste activated sludge at 55, 60 and 65°C, and fed with 13-C labelled and 12C-unlabelled acetate. Acetate uptake and cumulative methane production were determined and kinetic parameters were estimated using model-based analysis. Pyrosequencing performed on 13C- enriched samples indicated that organisms accumulating labelled carbon were Coprothermobacter (all temperatures between 55 and 65°C), acetoclastic Methanosarcina (55 to 60°C) and hydrogenotrophic Methanothermobacter (60 to 65°C). The increased relative abundance of Coprothermobacter with increased temperature corresponding with a shift to syntrophic acetate oxidation identified this as a potentially key oxidiser. Methanosarcina likely acts as both a hydrogen utilising and acetoclastic methanogen at 55°C, and is replaced by Methanothermobacter as a hydrogen utiliser at higher temperatures.

Characterisation of chlorophyll oxidation mediated by peroxidative activity in olives (Olea europaea L.) cv. Hojiblanca.

PubMed

Vergara-Domínguez, Honorio; Roca, María; Gandul-Rojas, Beatriz

2013-08-15

The oxidation of chlorophyll a (chl a) catalysed by peroxidase (POD) from mesocarp of the olive fruit (Olea europaea L., cv Hojiblanca) in the presence of H2O2 and 2,4-dichlorophenol (2,4-DCP), is characterised via the individualised quantification of the products of the enzymatic reaction using a new methodology of HPLC-UV spectrometry. This innovation has allowed the discovery that, in addition to 13(2) OH chl a and 15(1) OH lactone chl a, which are the first products of POD on chl a, the reaction process sequentially creates another series of oxidised chlorophyll derivatives which have not been previously described. Their origins have been linked to POD activity in the presence of 2,4-DCP. Likewise, a study of the effect of the concentration of the various cosubstrates on the POD reaction rate demonstrated that the correct establishment of the relative concentrations of the same ([H2O2]/[2,4-DCP]/[Chl]=1:3:0.02) is crucial to explaining inhibition effects by substrates and carrying out optimum measurements. Therefore, new essential parameters for the determination of POD activity on a chlorophyll substrate are established. Copyright © 2013 Elsevier Ltd. All rights reserved.

Combination of synchrotron radiation-based Fourier transforms infrared microspectroscopy and confocal laser scanning microscopy to understand spatial heterogeneity in aquatic multispecies biofilms.

PubMed

Reuben, Sheela; Banas, Krzysztof; Banas, Agnieszka; Swarup, Sanjay

2014-11-01

Understanding the spatial heterogeneity within environmental biofilms can provide an insight into compartmentalization of different functions in biofilm communities. We used a non-destructive and label-free method by combining Synchrotron Radiation-based Fourier Transform Infrared Microspectroscopy (SR-FTIR) with Confocal Laser Scanning Microscopy (CLSM) to distinguish the spatial chemical changes within multispecies biofilms grown from natural storm waters in flow cells. Among the different surfaces tested for biofilm growth and optimal imaging, mylar membranes were most suited and it enabled successful spatial infrared imaging of natural biofilms for obtaining reliable and interpretable FTIR spectra. Time series analysis of biofilm growth showed that influx of water during biofilm growth, results in significant changes in biofilm formation. Early biofilms showed active nutrient acquisition and desiccation tolerance mechanisms corresponding with accumulation of secreted proteins. Statistical approach used for the evaluation of chemical spectra allowed for clustering and classification of various regions of the biofilm. Microheterogeneity was observed in the polymeric components of the biofilm matrix, including cellulose, glycocalyx and dextran-like molecules. Fructan and glycan-rich regions were distinguishable and glycocalyx was abundant in the strongly adhering peripheral regions of biofilms. Inner core showed coexistence of oxygen dimers and ferrihydrite that will likely support growth of Fe (II)-oxidising bacteria. The combined SR-FTIR microspectroscopy and CSLM approach for complex natural biofilms described here will be useful both in understanding heterogeneity of matrix components and in correlating functions of juxtaposed microbial species in complex natural biofilms with physicochemical microenvironment to which they are exposed. Copyright © 2014 Elsevier Ltd. All rights reserved.

Deterioration of the anammox process at decreasing temperatures and long SRTs.

PubMed

Hoekstra, Maaike; de Weerd, Florence A; Kleerebezem, Robbert; van Loosdrecht, Mark C M

2018-03-01

The implementation of autotrophic nitrogen removal in the mainstream of a municipal wastewater treatment plant is currently pursued. Among the crucial unknown factors are the kinetic properties of anaerobic ammonium oxidising (anammox) bacteria at low temperatures. In this study we investigated the adaptation of a fast-growing anammox culture to a lower temperature. In a membrane bioreactor a highly enriched anammox community was obtained at 30°C, 25°C and 20°C. This culture was exposed to long- and short-term temperature changes. In short-term experiments the decrease in biomass-specific activity due to decrease in temperature can be described by an activation energy of 64 ± 28 kJ mol -1 . Prolonged cultivation (months) implies that cultivation at low temperatures resulted in deterioration of biomass-specific activity (Ea LT 239 kJ mol -1 ). The growth rate and specific anammox activity in the system decreased from 0.33 d -1 and 4.47 g NO 2 -N g VSS -1  d -1 at 30°C to 0.0011 d -1 and 0.037 g NO 2 -N g VSS -1  d -1 at 20°C. The reason for the deterioration of the system was related to the required long SRT in the system. The long SRT leads to an increase of non-active and non-anammox cells in the reactor, thereby decreasing the biomass-specific activity.

The effect of redox-active cyanomanganese(I) ligands on intramolecular electron transfer to, and alkyne alignment in, M(CO)(RC[triple bond, length as m-dash]CR)Tp' (M = Mo or W) units.

PubMed

Adams, Christopher J; Connelly, Neil G; Onganusorn, Sriwipha

2009-04-28

The complexes [(eta-C(5)Me(5))(ON)LMn(micro-CN)M(CO)(RC[triple bond, length as m-dash]CR)Tp'](+) (L = CNXyl, M = Mo; L = CNBu(t), M = Mo or W, R = Ph or Me) and trans- or cis-[(dppm){(EtO)(3)P}(OC)(2)Mn(micro-CN)M(CO)(PhC[triple bond, length as m-dash]CPh)Tp'](+), and their linkage isomers [(eta-C(5)Me(5))(ON)LMn(micro-NC)M(CO)(PhC[triple bond, length as m-dash]CPh)Tp'](+) and trans- or cis-[(dppm){(EtO)(3)P}(OC)(2)Mn(micro-NC)M(CO)(PhC[triple bond, length as m-dash]CPh)Tp'](+), undergo two one-electron oxidations. The complexes [(eta-C(5)Me(5))(ON)LMn(micro-XY)M(CO)(RC[triple bond, length as m-dash]CR)Tp'](+) (XY = CN or NC) are oxidised first at the N-bound metal centre and then at the C-bound centre. For [(dppm){(EtO)(3)P}(OC)(2)Mn(micro-XY)M(CO)(PhC[triple bond, length as m-dash]CPh)Tp'](+), the trans isomers are first oxidised at manganese whereas the cis isomers are first oxidised at M. Thus, the order of one-electron oxidation of the two series of binuclear monocations is influenced by linkage isomerisation of the cyanide bridge and cis-trans isomerisation of the Mn(CO)(2) group. IR spectroscopic changes on reaction of Ag(+) with [(eta-C(5)Me(5))(ON)(Bu(t)NC)Mn(micro-CN)W(CO)(MeC[triple bond, length as m-dash]CMe)Tp'](+) are consistent with one-electron at the N-bound tungsten centre. Likewise, trans-[(dppm){(EtO)(3)P}(OC)(2)Mn(micro-NC)M(CO)(PhC[triple bond, length as m-dash]CPh)Tp'](+) (M = Mo or W) give the stable dications [(dppm){(EtO)(3)P}(OC)(2)Mn(micro-NC)M(CO)(PhC[triple bond, length as m-dash]CPh)Tp'](2+). Significantly longer Mn-P bond distances in trans-[(dppm){(EtO)(3)P}(OC)(2)Mn(micro-NC)Mo(CO)(PhC[triple bond, length as m-dash]CPh)Tp'](2+) than in trans-[(dppm){(EtO)(3)P}(OC)(2)Mn(micro-NC)Mo(CO)(PhC[triple bond, length as m-dash]CPh)Tp'](+) are consistent with one-electron oxidation first at Mn(I); the alignment of the (CN)Mn(CO)(2){P(OEt)(3)}(dppm) fragment relative to the alkyne in trans-[(dppm){(EtO)(3)P}(OC)(2)Mn(micro-NC)Mo(CO)(PhC[triple bond, length as m-dash]CPh)Tp'](+) suggests it acts as a pi-acceptor, in contrast to related species such as trans-(NC)Mn(CO)(2){P(OEt)(3)}(dppm) and (NC)Mn(NO){P(OPh)(3)}(pi-C(5)H(4)Me) which behave as simple N-donors.

Multiple levels of regulation determine the role of the receptor for AGE (RAGE) as common soil in inflammation, immune responses and diabetes mellitus and its complications.

PubMed

Bierhaus, A; Nawroth, P P

2009-11-01

The pattern recognition receptor or receptor for AGE (RAGE) is constitutionally expressed in a few cell types only. However in almost all cells studied so far it is induced by reactions known to initiate inflammation. Its biological activity seems to be mainly dependent on the presence of its various ligands, including AGE, S100-calcium binding protein/calgranulins, high-mobility group protein 1, amyloid-beta-peptides and the family of beta-sheet fibrils, all known to be elevated in chronic metabolic, malignant and inflammatory diseases. The RAGE pathway interacts with cytokine-, lipopolysaccharide-, oxidised LDL- and glucose-triggered cellular reactions by turning a short-lasting inflammatory response into a sustained change of cellular function driven by perpetuated activation of the proinflammatory transcription factor, nuclear factor kappa-B. RAGE-mediated persistent cell activation is of pivotal importance in various experimental and clinical settings, including diabetes and its complications, neurodegeneration, ageing, tumour growth, and autoimmune and infectious inflammatory disease. Due to RAGE's central role in maintaining perpetuated cell activation, various therapeutic attempts to block RAGE or its ligands are currently under investigation. Despite broad experimental evidence for the role of RAGE in chronic disease, knowledge of its physiological function is still missing, limiting predictions about safety of long-term inhibition of RAGE x ligand interaction in chronic diseases.

Relating hygroscopicity and optical properties to chemical composition and structure of secondary organic aerosol particles generated from the ozonolysis of α-pinene

NASA Astrophysics Data System (ADS)

Denjean, C.; Formenti, P.; Picquet-Varrault, B.; Pangui, E.; Zapf, P.; Katrib, Y.; Giorio, C.; Tapparo, A.; Monod, A.; Temime-Roussel, B.; Decorse, P.; Mangeney, C.; Doussin, J. F.

2014-04-01

Secondary Organic Aerosol (SOA) were generated from the ozonolysis of α-pinene in the CESAM simulation chamber. The formation and ageing of the SOA were studied by following their optical, hygroscopic and chemical properties. The optical properties investigated by determining the particle Complex Refractive Index (CRI). The hygroscopicity was quantified by measuring the effect of RH on particle size (Growth Factor, GF) and scattering coefficient (f(RH)). The oxygen to carbon (O : C) atomic ratio of the particle surface and bulk were used as a sensitive parameter to correlate the changes in hygroscopic and optical properties of the SOA composition in CESAM. The real CRI at 525 nm wavelength decreased from 1.43-1.60 (±0.02) to 1.32-1.38 (±0.02) during the SOA formation. The decrease in real CRI correlates with a decrease in the O : C ratio of SOA from 0.68 (±0.20) to 0.55 (±0.16). In contrast, the GF stayed roughly constant over the reaction time, with values of 1.02-1.07 (±0.02) at 90% (±4.2) RH. Simultaneous measurements of O : C ratio of the particle surface revealed that the SOA was not composed of a homogeneous mixture, but with less oxidised species at the surface which would limit the water adsorption onto particle. In addition, an apparent change of both mobility diameter and scattering coefficient with increasing RH from 0 to 30% was observed for SOA after 16 h reaction. We postulate that this change could be due to a change in the viscosity of the SOA from a predominantly glassy state to a predominantly liquid state.

Aqueous cationic, anionic and non-ionic multi-walled carbon nanotubes, functionalised with minimal framework damage, for biomedical application

PubMed Central

Chen, Shu; Hu, Sheng; Smith, Elizabeth F.; Ruenraroengsak, Pakatip; Thorley, Andrew J.; Menzel, Robert; Goode, Angela E.; Ryan, Mary P.; Tetley, Teresa D.; Porter, Alexandra E.; Shaffer, Milo S. P.

2014-01-01

The use of a thermochemical grafting approach provides a versatile means to functionalise as-synthesised, bulk multi-walled carbon nanotubes (MWNTs) without altering their inherent structure. The associated retention of properties is desirable for a wide range of commercial applications, including for drug delivery and medical purposes; it is also pertinent to studies of intrinsic toxicology. A systematic series of water-compatible MWNTs, with diameter around 12 nm have been prepared, to provide structurally-equivalent samples predominantly stabilised by anionic, cationic, or non-ionic groups. The surface charge of MWNTs was controlled by varying the grafting reagents and subsequent post-functionalisation modifications. The degree of grafting was established by thermal analysis (TGA). High resolution transmission electron microscope (HRTEM) and Raman measurements confirmed that the structural framework of the MWNTs was unaffected by the thermochemical treatment, in contrast to a conventional acid-oxidised control which was severely damaged. The effectiveness of the surface modification was demonstrated by significantly improved solubility and stability in both water and cell culture medium, and further quantified by zeta-potential analysis. The grafted MWNTs exhibited relatively low bioreactivity on human immortal alveolar epithelial type 1-like cells (TT1) following 24h exposure as demonstrated by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) and lactate dehydrogenase release (LDH) assays. The exposure of TT1 cells to MWNTs suppressed the release of the inflammatory mediators, interleukin 6 (IL-6) and interleukin 8 (IL-8). TEM cell uptake studies indicated efficient cellular entry of MWNTs into TT1 cells, via a range of mechanisms. Cationic MWNTs showed a more substantial interaction with TT1 cell membranes than anionic MWNTs, demonstrating a surface charge effect on cell uptake. PMID:24631251

Ecohealth approach to urban waste management: exposure to environmental pollutants and health risks in Yamoussoukro, Côte d'Ivoire.

PubMed

Kouamé, Parfait K; Dongo, Kouassi; Nguyen-Viet, Hung; Zurbrügg, Christian; Lüthi, Christoph; Hattendorf, Jan; Utzinger, Jürg; Biémi, Jean; Bonfoh, Bassirou

2014-10-02

Poor waste management is a key driver of ill-health in urban settlements of developing countries. The current study aimed at assessing environmental and human health risks related to urban waste management in Yamoussoukro, the political capital of Côte d'Ivoire. We undertook trans-disciplinary research within an Ecohealth approach, comprised of a participatory workshop with stakeholders and mapping of exposure patterns. A total of 492 randomly selected households participated in a cross-sectional survey. Waste deposit sites were characterised and 108 wastewater samples were subjected to laboratory examinations. The physico-chemical parameters of the surface water (temperature, pH, conductivity, potential oxidise reduction, BOD5, COD, dissolved oxygen, nitrates, ammonia and total Kendal nitrogen) did not comply with World Health Organization standards of surface water quality. Questionnaire results showed that malaria was the most commonly reported disease. Diarrhoea and malaria were associated with poor sanitation. Households having dry latrines had a higher risk of diarrhoea (odds ratio (OR) = 1.8, 95% confidence interval (CI) 1.2-2.7) compared to latrines with septic tanks and also a higher risk for malaria (OR = 1.9, 95% (CI) 1.1-3.3). Our research showed that combining health and environmental assessments enables a deeper understanding of environmental threats and disease burdens linked to poor waste management. Further study should investigate the sanitation strategy aspects that could reduce the environmental and health risks in the study area.

Ecohealth Approach to Urban Waste Management: Exposure to Environmental Pollutants and Health Risks in Yamoussoukro, Côte d’Ivoire

PubMed Central

Kouamé, Parfait K.; Dongo, Kouassi; Nguyen-Viet, Hung; Zurbrügg, Christian; Lüthi, Christoph; Hattendorf, Jan; Utzinger, Jürg; Biémi, Jean; Bonfoh, Bassirou

2014-01-01

Poor waste management is a key driver of ill-health in urban settlements of developing countries. The current study aimed at assessing environmental and human health risks related to urban waste management in Yamoussoukro, the political capital of Côte d’Ivoire. We undertook trans-disciplinary research within an Ecohealth approach, comprised of a participatory workshop with stakeholders and mapping of exposure patterns. A total of 492 randomly selected households participated in a cross-sectional survey. Waste deposit sites were characterised and 108 wastewater samples were subjected to laboratory examinations. The physico-chemical parameters of the surface water (temperature, pH, conductivity, potential oxidise reduction, BOD5, COD, dissolved oxygen, nitrates, ammonia and total Kendal nitrogen) did not comply with World Health Organization standards of surface water quality. Questionnaire results showed that malaria was the most commonly reported disease. Diarrhoea and malaria were associated with poor sanitation. Households having dry latrines had a higher risk of diarrhoea (odds ratio (OR) = 1.8, 95% confidence interval (CI) 1.2–2.7) compared to latrines with septic tanks and also a higher risk for malaria (OR = 1.9, 95% (CI) 1.1–3.3). Our research showed that combining health and environmental assessments enables a deeper understanding of environmental threats and disease burdens linked to poor waste management. Further study should investigate the sanitation strategy aspects that could reduce the environmental and health risks in the study area. PMID:25279545

Redox responses are preserved across muscle fibres with differential susceptibility to aging.

PubMed

Smith, Neil T; Soriano-Arroquia, Ana; Goljanek-Whysall, Katarzyna; Jackson, Malcolm J; McDonagh, Brian

2018-04-15

Age-related loss of muscle mass and function is associated with increased frailty and loss of independence. The mechanisms underlying the susceptibility of different muscle types to age-related atrophy are not fully understood. Reactive oxygen species (ROS) are recognised as important signalling molecules in healthy muscle and redox sensitive proteins can respond to intracellular changes in ROS concentrations modifying reactive thiol groups on Cysteine (Cys) residues. Conserved Cys residues tend to occur in functionally important locations and can have a direct impact on protein function through modifications at the active site or determining protein conformation. The aim of this work was to determine age-related changes in the redox proteome of two metabolically distinct murine skeletal muscles, the quadriceps a predominantly glycolytic muscle and the soleus which contains a higher proportion of mitochondria. To examine the effects of aging on the global proteome and the oxidation state of individual redox sensitive Cys residues, we employed a label free proteomics approach including a differential labelling of reduced and reversibly oxidised Cys residues. Our results indicate the proteomic response to aging is dependent on muscle type but redox changes that occur primarily in metabolic and cytoskeletal proteins are generally preserved between metabolically distinct tissues. Skeletal muscle containing fast twitch glycolytic fibres are more susceptible to age related atrophy compared to muscles with higher proportions of oxidative slow twitch fibres. Contracting skeletal muscle generates reactive oxygen species that are required for correct signalling and adaptation to exercise and it is also known that the intracellular redox environment changes with age. To identify potential mechanisms for the distinct response to age, this article combines a global proteomic approach and a differential labelling of reduced and reversibly oxidised Cysteine residues in two metabolically distinct skeletal muscles, quadriceps and soleus, from adult and old mice. Our results indicate that the global proteomic changes with age in skeletal muscles are dependent on fibre type. However, redox specific changes are preserved across muscle types and accompanied with a reduction in the number of redox sensitive Cysteine residues. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

The Role of Oxidoreductases in Determining the Function of the Neisserial Lipid A Phosphoethanolamine Transferase Required for Resistance to Polymyxin

PubMed Central

Piek, Susannah; Wang, Zhirui; Ganguly, Jhuma; Lakey, Adam M.; Bartley, Stephanie N.; Mowlaboccus, Shakeel; Anandan, Anandhi; Stubbs, Keith A.; Scanlon, Martin J.; Vrielink, Alice; Azadi, Parastoo; Carlson, Russell W.; Kahler, Charlene M.

2014-01-01

The decoration of the lipid A headgroups of the lipooligosaccharide (LOS) by the LOS phosphoethanolamine (PEA) transferase (LptA) in Neisseria spp. is central for resistance to polymyxin. The structure of the globular domain of LptA shows that the protein has five disulphide bonds, indicating that it is a potential substrate of the protein oxidation pathway in the bacterial periplasm. When neisserial LptA was expressed in Escherichia coli in the presence of the oxidoreductase, EcDsbA, polymyxin resistance increased 30-fold. LptA decorated one position of the E. coli lipid A headgroups with PEA. In the absence of the EcDsbA, LptA was degraded in E. coli. Neisseria spp. express three oxidoreductases, DsbA1, DsbA2 and DsbA3, each of which appear to donate disulphide bonds to different targets. Inactivation of each oxidoreductase in N. meningitidis enhanced sensitivity to polymyxin with combinatorial mutants displaying an additive increase in sensitivity to polymyxin, indicating that the oxidoreductases were required for multiple pathways leading to polymyxin resistance. Correlates were sought between polymyxin sensitivity, LptA stability or activity and the presence of each of the neisserial oxidoreductases. Only meningococcal mutants lacking DsbA3 had a measurable decrease in the amount of PEA decoration on lipid A headgroups implying that LptA stability was supported by the presence of DsbA3 but did not require DsbA1/2 even though these oxidoreductases could oxidise the protein. This is the first indication that DsbA3 acts as an oxidoreductase in vivo and that multiple oxidoreductases may be involved in oxidising the one target in N. meningitidis. In conclusion, LptA is stabilised by disulphide bonds within the protein. This effect was more pronounced when neisserial LptA was expressed in E. coli than in N. meningitidis and may reflect that other factors in the neisserial periplasm have a role in LptA stability. PMID:25215579

Biochemical effects and growth inhibition in MCF-7 cells caused by novel sulphonamido oxa-polyamine derivatives.

PubMed

Pavlov, V; Lin, P Kong Thoo; Rodilla, V

2002-04-01

The novel polyamine derivatives sulphonamido oxa-spermine (oxa-Spm) and sulphonamido oxa-spermidine (oxa-Spd) exhibited rapid cytotoxic action towards MCF-7 human breast cancer cells with IC50 values of 4.35 and 6.47 pM, respectively, after 24-h drug exposure. Neither compound is a substrate of serum amine oxidase. Both oxa-Spm and oxa-Spd caused cell shrinkage, as determined by phase-contrast microscopy. After incubation with 10 microM of either compound for 8 h, the cells underwent chromatin condensation and nuclear fragmentation. However, no clear DNA ladder was obtained by electrophoresis. The sulphonamido oxa-polyamine derivatives and especially oxa-Spd enhanced the activity of polyamine oxidase (PAO), an enzyme capable of oxidising N1-acetylated spermine and spermidine to spermidine and putrescine, respectively, generating cytotoxic H2O2 and 3-acetamidopropanal as by-products. The intracellular polyamine content was only marginally reduced in response to drug treatment. In conclusion, our data show that these novel sulphonamido oxa-polyamine derivatives possess high cytotoxic activity against MCF-7 cells and indicate that induction of PAO may mediate their cytotoxicity via apoptosis.

Inhibitory effect of Piper betel leaf extracts on copper-mediated LDL oxidation and oxLDL-induced lipid accumulation via inducing reverse cholesterol transport in macrophages.

PubMed

Ma, Gwo-Chin; Wu, Pei-Fang; Tseng, Hsien-Chun; Chyau, Charng-Cherng; Lu, Hsiu-Chin; Chou, Fen-Pi

2013-12-15

Piper betel leaf (PBL) has the biological capabilities of detoxification and can work as an anti-inflammatory agent and an anti-oxidant. In this study, we evaluated the anti-oxidative activity of the extract of Piper betel leaves (PBLs) on the basis of Cu(2+)-mediated oxidation, and its ability to prevent foam cell formation in a model for oxidised low density lipoprotein (oxLDL)-induced lipid accumulation in macrophages. Our data demonstrated that PBLs were able to inhibit LDL oxidation in vitro and are able to reduce the lipid accumulation in macrophages. We showed the underlying mechanisms to be the following: PBLs up-regulated the protein levels of the class A and class B scavenger receptors, the membrane lipid transporter ABCA1, and its upstream regulator Liver X receptor (LXR) in the macrophages exposed to oxLDL. The results suggested that PBLs activated the reverse cholesterol transport mechanism to enhance the metabolism of the oxLDL that could prevent both lipid accumulation and foam cell formation and further minimise the possible damage of vessels caused by the oxLDL. Copyright © 2013 Elsevier Ltd. All rights reserved.

(234)U/(238)U signatures associated with uranium ore bodies: part 2 Manyingee.

PubMed

Lowson, Richard T; McIntyre, Mark G

2013-04-01

The Manyingee ore body is a roll-front U ore body located at depth in the Cretaceous sandstone sediments of a Proterozoic palaeo valley. It is located in a confined aquifer. The aquifer is recharged 4 km upstream by the Ashburton River. Groundwater samples were collected at and up to 4.7 km downstream of the ore body. The ground water (234)U/(238)U activity ratios (AR) were elevated to 1.86 in the vicinity of the ore body and then declined to 1.06 over the 4.7 km transect. The elevated (234)U/(238)U ARs are attributed to selective leaching of (234)U sites by oxidising waters, with α recoil as a necessary precursor to produce activated (234)U sites. Direct ejection into another phase following α recoil is considered to be a minor contributor to (234)U -(238)U disequilibrium in this environment. The profile is considered to be typical of the (234)U/(238)U AR profile at and down gradient of the redox front of a U ore body. Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.

Copahue Geothermal System: A Volcanic Environment with Rich Extreme Prokaryotic Biodiversity

PubMed Central

Urbieta, María Sofía; Willis Porati, Graciana; Segretín, Ana Belén; González-Toril, Elena; Giaveno, María Alejandra; Donati, Edgardo Rubén

2015-01-01

The Copahue geothermal system is a natural extreme environment located at the northern end of the Cordillera de los Andes in Neuquén province in Argentina. The geochemistry and consequently the biodiversity of the area are dominated by the activity of the Copahue volcano. The main characteristic of Copahue is the extreme acidity of its aquatic environments; ponds and hot springs of moderate and high temperature as well as Río Agrio. In spite of being an apparently hostile location, the prokaryotic biodiversity detected by molecular ecology techniques as well as cultivation shows a rich and diverse environment dominated by acidophilic, sulphur oxidising bacteria or archaea, depending on the conditions of the particular niche studied. In microbial biofilms, found in the borders of the ponds where thermal activity is less intense, the species found are completely different, with a high presence of cyanobacteria and other photosynthetic species. Our results, collected during more than 10 years of work in Copahue, have enabled us to outline geomicrobiological models for the different environments found in the ponds and Río Agrio. Besides, Copahue seems to be the habitat of novel, not yet characterised autochthonous species, especially in the domain Archaea. PMID:27682093

A novel bioreactor system for simultaneous mutli-metal leaching from industrial pyrite ash: Effect of agitation and sulphur dosage.

PubMed

Panda, Sandeep; Akcil, Ata; Mishra, Srabani; Erust, Ceren

2018-01-15

Simultaneous multi-metal leaching from industrial pyrite ash is reported for the first time using a novel bioreactor system that allows natural diffusion of atmospheric O 2 and CO 2 along with the required temperature maintenance. The waste containing economically important metals (Cu, Co, Zn & As) was leached using an adapted consortium of meso-acidophilic Fe 2+ and S oxidising bacteria. The unique property of the sample supported adequate growth and activity of the acidophiles, thereby, driving the (bio) chemical reactions. Oxido-reductive potentials were seen to improve with time and the system's pH lowered as a result of active S oxidation. Increase in sulphur dosage (>1g/L) and agitation speed (>150rpm) did not bear any significant effect on metal dissolution. The consortium was able to leach 94.01% Cu (11.75% dissolution/d), 98.54% Co (12.3% dissolution/d), 75.95% Zn (9.49% dissolution/d) and 60.80% As (7.6% dissolution/d) at 150rpm, 1g/L sulphur, 30°C in 8days. Copyright © 2017 Elsevier B.V. All rights reserved.

Copahue Geothermal System: A Volcanic Environment with Rich Extreme Prokaryotic Biodiversity.

PubMed

Urbieta, María Sofía; Porati, Graciana Willis; Segretín, Ana Belén; González-Toril, Elena; Giaveno, María Alejandra; Donati, Edgardo Rubén

2015-07-08

The Copahue geothermal system is a natural extreme environment located at the northern end of the Cordillera de los Andes in Neuquén province in Argentina. The geochemistry and consequently the biodiversity of the area are dominated by the activity of the Copahue volcano. The main characteristic of Copahue is the extreme acidity of its aquatic environments; ponds and hot springs of moderate and high temperature as well as Río Agrio. In spite of being an apparently hostile location, the prokaryotic biodiversity detected by molecular ecology techniques as well as cultivation shows a rich and diverse environment dominated by acidophilic, sulphur oxidising bacteria or archaea, depending on the conditions of the particular niche studied. In microbial biofilms, found in the borders of the ponds where thermal activity is less intense, the species found are completely different, with a high presence of cyanobacteria and other photosynthetic species. Our results, collected during more than 10 years of work in Copahue, have enabled us to outline geomicrobiological models for the different environments found in the ponds and Río Agrio. Besides, Copahue seems to be the habitat of novel, not yet characterised autochthonous species, especially in the domain Archaea.

Structural characterization of encapsulated ferritin provides insight into iron storage in bacterial nanocompartments

PubMed Central

He, Didi; Hughes, Sam; Vanden-Hehir, Sally; Georgiev, Atanas; Altenbach, Kirsten; Tarrant, Emma; Mackay, C Logan; Waldron, Kevin J; Clarke, David J; Marles-Wright, Jon

2016-01-01

Ferritins are ubiquitous proteins that oxidise and store iron within a protein shell to protect cells from oxidative damage. We have characterized the structure and function of a new member of the ferritin superfamily that is sequestered within an encapsulin capsid. We show that this encapsulated ferritin (EncFtn) has two main alpha helices, which assemble in a metal dependent manner to form a ferroxidase center at a dimer interface. EncFtn adopts an open decameric structure that is topologically distinct from other ferritins. While EncFtn acts as a ferroxidase, it cannot mineralize iron. Conversely, the encapsulin shell associates with iron, but is not enzymatically active, and we demonstrate that EncFtn must be housed within the encapsulin for iron storage. This encapsulin nanocompartment is widely distributed in bacteria and archaea and represents a distinct class of iron storage system, where the oxidation and mineralization of iron are distributed between two proteins. DOI: http://dx.doi.org/10.7554/eLife.18972.001 PMID:27529188

Protein CoAlation: a redox-regulated protein modification by coenzyme A in mammalian cells

PubMed Central

Tsuchiya, Yugo; Peak-Chew, Sew Yeu; Newell, Clare; Miller-Aidoo, Sheritta; Mangal, Sriyash; Zhyvoloup, Alexander; Bakovic´, Jovana; Malanchuk, Oksana; Pereira, Gonçalo C.; Kotiadis, Vassilios; Szabadkai, Gyorgy; Duchen, Michael R.; Campbell, Mark; Cuenca, Sergio Rodriguez; Vidal-Puig, Antonio; James, Andrew M.; Murphy, Michael P.; Filonenko, Valeriy; Skehel, Mark

2017-01-01

Coenzyme A (CoA) is an obligatory cofactor in all branches of life. CoA and its derivatives are involved in major metabolic pathways, allosteric interactions and the regulation of gene expression. Abnormal biosynthesis and homeostasis of CoA and its derivatives have been associated with various human pathologies, including cancer, diabetes and neurodegeneration. Using an anti-CoA monoclonal antibody and mass spectrometry, we identified a wide range of cellular proteins which are modified by covalent attachment of CoA to cysteine thiols (CoAlation). We show that protein CoAlation is a reversible post-translational modification that is induced in mammalian cells and tissues by oxidising agents and metabolic stress. Many key cellular enzymes were found to be CoAlated in vitro and in vivo in ways that modified their activities. Our study reveals that protein CoAlation is a widespread post-translational modification which may play an important role in redox regulation under physiological and pathophysiological conditions. PMID:28341808

Skin protection against UVA-induced iron damage by multiantioxidants and iron chelating drugs/prodrugs.

PubMed

Reelfs, Olivier; Eggleston, Ian M; Pourzand, Charareh

2010-03-01

In humans, prolonged sunlight exposure is associated with various pathological states. The continuing drive to develop improved skin protection involves not only approaches to reduce DNA damage by solar ultraviolet B (UVB) but also the development of methodologies to provide protection against ultraviolet A (UVA), the oxidising component of sunlight. Furthermore identification of specific cellular events following ultraviolet (UV) irradiation is likely to provide clues as to the mechanism of the development of resulting pathologies and therefore strategies for protection. Our discovery that UVA radiation, leads to an immediate measurable increase in 'labile' iron in human skin fibroblasts and keratinocytes provides a new insight into UVA-induced skin damage, since iron is a catalyst of biological oxidations. The main purpose of this overview is to bring together some of the new findings related to mechanisms underlying UVA-induced iron release and to discuss novel approaches based on the use of multiantioxidants and light-activated caged-iron chelators for efficient protection of skin cells against UVA-induced iron damage.

Simultaneous photodegradation of VOC mixture by TiO2 powders.

PubMed

Stucchi, Marta; Galli, Federico; Bianchi, Claudia L; Pirola, Carlo; Boffito, Daria C; Biasioli, Franco; Capucci, Valentino

2018-02-01

Volatile and semi volatile organic compounds' concentration have dramatically increased in indoor environments in recent years. UV light promotes titanium dioxide, which oxidises various molecules; however, most of the studies report the degradation of a single VOC. Here, we investigate the photo-oxidation of 17 molecules in mixture to have a realistic test of TiO 2 efficacy. We compare P25, a nanometric catalyst, and 1077, a micrometric sample, that poses less health concerns. A proton-transfer-reaction mass spectrometer measured online the concentration of all the pollutants simultaneously. Aldehydes compete for the adsorption on both the catalyst's active sites and thus they degrade 70% and 55% with P25 and 1077 respectively. Considering the single pollutant oxidation, instead, aldehydes fully oxidize. Even though benzene is recalcitrant to degradation, P25 and 1077 reduced toluene's concentration to 97% and 96% in 55 min, respectively. Acetonitrile is refractory to photocatalysis. Copyright © 2017. Published by Elsevier Ltd.

[Chronic renal disease as cardiovascular risk factor].

PubMed

Hermans, M M H; Kooman, J P; Stehouwer, C D A

2008-07-19

A lowering of the glomerular filtration rate (GFR) and/or the presence of albuminuria are signs of chronic renal disease. Both variables are for the most part independently associated with an increased risk of cardiovascular morbidity and mortality. Albuminuria is a marker of endothelial dysfunction. A decrease of the GFR is associated with non-traditional risk factors, e.g. renal anaemia, uraemic toxins due to a decrease of the renal clearance, hyperhomocysteinaemia caused by a diminished homocysteine metabolism, excessive activation of the sympathetic nervous system which is related to sleep apnoea syndrome, oxidative stress and dyslipidaemia associated with the formation of vasotoxic, oxidised LDL cholesterol. These non-traditional risk factors may, alone or in combination with traditional atherogenic risk factors (e.g. age, male gender, smoking, hypercholesterolaemia, hypertension, obesity, positive family history and diabetes mellitus), partially via endothelial dysfunction, result in harmful effects on arterial function, increasing cardiovascular morbidity and mortality. Different stages of chronic kidney disease are associated with specific risk factors, making a specific therapeutic approach essential.

What does the Sr-substituted 2.1 Å resolution crystal structure of photosystem II reveal about the water oxidation mechanism?

PubMed

Terrett, Richard; Petrie, Simon; Pace, Ron J; Stranger, Robert

2014-03-25

A density functional study of the Sr-substituted photosystem II water oxidising complex demonstrates that its recent X-ray crystal structure is consistent with a (Mn(III))4 oxidation state pattern, and with a Sr-bound hydroxide ion. The Sr-water-hydroxide interactions rationalize differences in the exchange rates of substrate water and kinetics of dioxygen bond formation relative to the Ca-containing structure.

Ozonation of hospital raw wastewaters for cytostatic compounds removal. Kinetic modelling and economic assessment of the process.

PubMed

Ferre-Aracil, J; Valcárcel, Y; Negreira, N; de Alda, M López; Barceló, D; Cardona, S C; Navarro-Laboulais, J

2016-06-15

The kinetics of the ozone consumption for the pretreatment of hospital wastewater has been analysed in order to determine the reaction rate coefficients between the ozone and the readily oxidisabled organic matter and cytostatic compounds. The wastewater from a medium size hospital was treated with ozone and peroxone methodologies, varying the ozone concentration, the reaction time and the hydrogen peroxide doses. The analysis shows that there are four cytostatic compounds, i.e. irinotecan, ifosfamide, cyclophosphamide and capecitabine, detected in the wastewaters and they are completely removed with reasonably short times after the ozone treatment. Considering the reactor geometry, the gas hydrodynamics, the mass transfer of ozone from gas to liquid and the reaction of all oxidisable compounds of the wastewater it is possible to determine the chemical ozone demand, COzD, of the sample as 256mgO3L(-1) and the kinetic rate coefficient with the dissolved organic matter as 8.4M(-1)s(-1). The kinetic rate coefficient between the ozone and the cyclophosphamide is in the order of 34.7M(-1)s(-1) and higher for the other cytostatics. The direct economic cost of the treatment was evaluated considering this reaction kinetics and it is below 0.3€/m(3) under given circumstances. Copyright © 2016 Elsevier B.V. All rights reserved.

N2O emission characteristics and its affecting factors in rain-fed potato fields in Wuchuan County, China

NASA Astrophysics Data System (ADS)

Wang, Liwei; Wang, Cheng; Pan, Zhihua; Xu, Hui; Gao, Lin; Zhao, Peiyi; Dong, Zhiqiang; Zhang, Jingting; Cui, Guohui; Wang, Sen; Han, Guolin; Zhao, hui

2017-05-01

Representing an important greenhouse gas, nitrous oxide (N2O) emission from cultivated land is a hot topic in current climate change research. This study examined the influences of nitrogen fertilisation, temperature and soil moisture on the ammonia monooxygenase subunit A ( amoA) gene copy numbers and N2O emission characteristics. The experimental observation of N2O fluxes was based on the static chamber-gas chromatographic method. The ammonia-oxidising bacteria (AOB) and ammonia-oxidising archaea (AOA) gene copy numbers in different periods were measured by real-time polymerase chain reaction (PCR). The results indicated that rain-fed potato field was a N2O source, and the average annual N2O emission was approximately 0.46 ± 0.06 kgN2O-N/ha/year. N2O emissions increased significantly with increase in fertilisation, temperatures below 19.6 °C and soil volumetric water content under 15%. Crop rotation appreciably decreases N2O emissions by 34.4 to 52.4% compared to continuous cropping in rain-fed potato fields. The significant correlation between N2O fluxes and AOB copy numbers implied that N2O emissions were primarily controlled by AOB in rain-fed potato fields. The research has important theoretical and practical value for understanding N2O emissions from rain-fed dry farmland fields.

Diet affects the redox system in developing Atlantic cod (Gadus morhua) larvae.

PubMed

Penglase, Samuel; Edvardsen, Rolf B; Furmanek, Tomasz; Rønnestad, Ivar; Karlsen, Ørjan; van der Meeren, Terje; Hamre, Kristin

2015-08-01

The growth and development of marine fish larvae fed copepods is superior to those fed rotifers, but the underlying molecular reasons for this are unclear. In the following study we compared the effects of such diets on redox regulation pathways during development of Atlantic cod (Gadus morhua) larvae. Cod larvae were fed a control diet of copepods or the typical rotifer/Artemia diet commonly used in commercial marine fish hatcheries, from first feeding until after metamorphosis. The oxidised and reduced glutathione levels, the redox potential, and the mRNA expression of 100 genes in redox system pathways were then compared between treatments during larval development. We found that rotifer/Artemia-fed cod larvae had lower levels of oxidised glutathione, a more reduced redox potential, and altered expression of approximately half of the redox system genes when compared to copepod-fed larvae. This rotifer/Artemia diet-induced differential regulation of the redox system was greatest during periods of suboptimal growth. Upregulation of the oxidative stress response transcription factor, nrf2, and NRF2 target genes in rotifer/Artemia fed larvae suggest this diet induced an NRF2-mediated oxidative stress response. Overall, the data demonstrate that nutritional intake plays a role in regulating the redox system in developing fish larvae. This may be a factor in dietary-induced differences observed in larval growth. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

HPLC-MS degradation study of E10 Sunset Yellow FCF in a commercial beverage.

PubMed

Gosetti, Fabio; Gianotti, Valentina; Polati, Stefano; Gennaro, Maria Carla

2005-10-07

Experimental evidence has shown that a beverage containing Sunset Yellow FCF (labelled as E110 in the European Union), when exposed to natural conditions of summer temperature and sunlight, losses its colour. To possibly identify the degradation pathway and collect information on the potential toxicity of the uncoloured species formed, different degradation conditions, under both oxidising and reducing environments, were simulated in laboratory. Experiments were carried out under the following conditions: (i) thermally induced degradation, (ii) visible photo induced degradation, (iii) UV-photo induced conditions in oxidising environment (addition of hydrogen peroxide, Fenton reaction) and (iv) UV-photo induced conditions in reducing environment (addition of sulphide and ascorbic acid, addition of ascorbic acid in the absence and in the presence of saccharose). Decolourisation process was observed in oxidant conditions when applying the Fenton reaction but the reaction was too quick to be progressively followed. On the other hand, it was also possible to study the degradation reaction observed in reducing conditions in the presence of ascorbic acid. The HPLC-MS results gave evidence for the cleavage of the double bond and the protonation of the azo groups. The loss of colour is therefore not due to a mineralization process but to the formation of a dimeric form of 5-amino-6-hydroxy-2-naphthalene sulfonate and, likely, of p-amino-benzensulfonate.

Aflatoxin B1 can be complexed with oxidised tea polyphenols and the absorption of the complexed aflatoxin B1 is inhibited in rats.

PubMed

Lu, Hao; Liu, Feifei; Zhu, Qiangqiang; Zhang, Mengmeng; Li, Tong; Chen, Jiming; Huang, Yewei; Wang, Xuanjun; Sheng, Jun

2017-04-01

Aflatoxin B1 (AFB1) is the most prevalent and carcinogenic form of the aflatoxins. In this report, we explored the interaction between AFB1 and oxidised tea polyphenols (OTP). Then, the influence of OTP on the absorption and toxicity of AFB1 in rats was investigated. We found that AFB1 can be complexed with OTP, and a transmembrane bidirectional transport experiment verified the absorption of complexed AFB1 (C-AFB1) was inhibited by OTP dramatically (P < 0.001). Animal experiments results showed that the AFB1 plus OTP group had significantly (P < 0.05) decreased AFB1-albumin (AFB1-alb) compared to the AFB1 group at 4 h after ingestion. OTP could significantly (P < 0.01) promote the elimination of AFB1 in faeces. Moreover, the liver injury induced by AFB1 was significantly inhibited by OTP. Our results demonstrated AFB1 can be complexed with OTP and the absorption of the C-AFB1 is inhibited in rats. Consequently, the liver injury induced by AFB1 can be inhibited by OTP. These results provide insight that consuming OTP-containing products, like fermented Pu-er tea, can protect damage from AFB1, and OTP may be used as a kind of food additive. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Tungsten phosphanylarylthiolato complexes [W{PhP(2-SC6H4)2-kappa3S,S',P} 2] and [W{P(2-SC6H4)3-kappa4S,S',S",P}2]: synthesis, structures and redox chemistry.

PubMed

Hildebrand, Alexandra; Lönnecke, Peter; Silaghi-Dumitrescu, Luminita; Hey-Hawkins, Evamarie

2008-09-14

PhP(2-SHC6H4)2 (PS2H2) reacts with WCl6 with reduction of tungsten to give the air-sensitive tungsten(IV) complex [W{PhP(2-SC6H4)2-kappa(3)S,S',P}2] (1). 1 is oxidised in air to [WO{PhPO(2-SC6H4)2-kappa(3)S,S',O}{PhP(2-SC6H4)2-kappa(3)S,S',P}] (2). The attempted synthesis of 2 by reaction of 1 with iodosobenzene as oxidising agent was unsuccessful. [W{P(2-SC6H4)3-kappa(4)S,S',S",P}2] (3) was formed in the reaction of P(2-SHC6H4)3 (PS3H3) with WCl6. The W(VI) complex 3 contains two PS3(3-) ligands, each coordinated in a tetradentate fashion resulting in a tungsten coordination number of eight. The reaction of 3 with AgBF4 yields the dinuclear tungsten complex [W2{P(2-SC6H4)3-kappa(4)S,S',S",P}3]BF4 (4). Complexes 1-4 were characterised by spectral methods and X-ray structure determination.

Evaluating the potential impact of proton carriers on syntrophic propionate oxidation

PubMed Central

Juste-Poinapen, Natacha M. S.; Turner, Mark S.; Rabaey, Korneel; Virdis, Bernardino; Batstone, Damien J.

2015-01-01

Anaerobic propionic acid degradation relies on interspecies electron transfer (IET) between propionate oxidisers and electron acceptor microorganisms, via either molecular hydrogen, formate or direct transfers. We evaluated the possibility of stimulating direct IET, hence enhancing propionate oxidation, by increasing availability of proton carriers to decrease solution resistance and reduce pH gradients. Phosphate was used as a proton carrying anion, and chloride as control ion together with potassium as counter ion. Propionic acid consumption in anaerobic granules was assessed in a square factorial design with ratios (1:0, 2:1, 1:1, 1:2 and 0:1) of total phosphate (TP) to Cl−, at 1X, 10X, and 30X native conductivity (1.5 mS.cm−1). Maximum specific uptake rate, half saturation, and time delay were estimated using model-based analysis. Community profiles were analysed by fluorescent in situ hybridisation and 16S rRNA gene pyrosequencing. The strongest performance was at balanced (1:1) ratios at 10X conductivity where presumptive propionate oxidisers namely Syntrophobacter and Candidatus Cloacamonas were more abundant. There was a shift from Methanobacteriales at high phosphate, to Methanosaeta at low TP:Cl ratios and low conductivity. A lack of response to TP, and low percentage of presumptive electroactive organisms suggested that DIET was not favoured under the current experimental conditions. PMID:26670292

Links between sulphur oxidation and sulphur-oxidising bacteria abundance and diversity in soil microcosms based on soxB functional gene analysis.

PubMed

Tourna, Maria; Maclean, Paul; Condron, Leo; O'Callaghan, Maureen; Wakelin, Steven A

2014-06-01

Sulphur-oxidising bacteria (SOB) play a key role in the biogeochemical cycling of sulphur in soil ecosystems. However, the ecology of SOB is poorly understood, and there is little knowledge about the taxa capable of sulphur oxidation, their distribution, habitat preferences and ecophysiology. Furthermore, as yet there are no conclusive links between SOB community size or structure and rates of sulphur oxidation. We have developed a molecular approach based on primer design targeting the soxB functional gene of nonfilamentous chemolithotrophic SOB that allows assessment of both abundance and diversity. Cloning and sequencing revealed considerable diversity of known soxB genotypes from agricultural soils and also evidence for previously undescribed taxa. In a microcosm experiment, abundance of soxB genes increased with sulphur oxidation rate in soils amended with elemental sulphur. Addition of elemental sulphur to soil had a significant effect in the soxB gene diversity, with the chemolithotrophic Thiobacillus-like Betaproteobacteria sequences dominating clone libraries 6 days after sulphur application. Using culture-independent methodology, the study provides evidence for links between abundance and diversity of SOB and sulphur oxidation. The methodology provides a new tool for investigation of the ecology and role of SOB in soil sulphur biogeochemistry. © 2014 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

N2O emission characteristics and its affecting factors in rain-fed potato fields in Wuchuan County, China.

PubMed

Wang, Liwei; Wang, Cheng; Pan, Zhihua; Xu, Hui; Gao, Lin; Zhao, Peiyi; Dong, Zhiqiang; Zhang, Jingting; Cui, Guohui; Wang, Sen; Han, Guolin; Zhao, Hui

2017-05-01

Representing an important greenhouse gas, nitrous oxide (N 2 O) emission from cultivated land is a hot topic in current climate change research. This study examined the influences of nitrogen fertilisation, temperature and soil moisture on the ammonia monooxygenase subunit A (amoA) gene copy numbers and N 2 O emission characteristics. The experimental observation of N 2 O fluxes was based on the static chamber-gas chromatographic method. The ammonia-oxidising bacteria (AOB) and ammonia-oxidising archaea (AOA) gene copy numbers in different periods were measured by real-time polymerase chain reaction (PCR). The results indicated that rain-fed potato field was a N 2 O source, and the average annual N 2 O emission was approximately 0.46 ± 0.06 kgN 2 O-N/ha/year. N 2 O emissions increased significantly with increase in fertilisation, temperatures below 19.6 °C and soil volumetric water content under 15%. Crop rotation appreciably decreases N 2 O emissions by 34.4 to 52.4% compared to continuous cropping in rain-fed potato fields. The significant correlation between N 2 O fluxes and AOB copy numbers implied that N 2 O emissions were primarily controlled by AOB in rain-fed potato fields. The research has important theoretical and practical value for understanding N 2 O emissions from rain-fed dry farmland fields.

The role of allophane nano-structure and Fe oxide speciation for hosting soil organic matter in an allophanic Andosol

NASA Astrophysics Data System (ADS)

Filimonova, Svetlana; Kaufhold, Stephan; Wagner, Friedrich E.; Häusler, Werner; Kögel-Knabner, Ingrid

2016-05-01

We evaluated the impact of nano-structural characteristics of allophanic compounds and Fe oxide speciation on the efficiency of organo-mineral interactions in an allophanic Andosol derived from volcanic ash (Eifel mountains, Germany). The samples selected for our work represented a gradient from: (i) a pure synthetic allophane and (ii) model organo-mineral mixtures to (iii) particle size fractions of the natural Andosol. We thus aimed to link the processes operating at the individual molecular scale to the phenomena active at the aggregate scale. For a non-destructive characterization of the samples, we applied 129Xe NMR spectroscopy of adsorbed Xe atoms (to identify the mineral nano-structure and surface acid centres), ESEM (verifying the nano-spherical structure of allophane), 13C CPMAS NMR (for the nature of the soil organic matter (SOM)), 57Fe Mössbauer spectroscopy (Fe oxide speciation), and N2 adsorption (contribution of micro- and mesoporosity). By using the atomic probe Xe, we obtained evidence for a coupled mechanism of adsorption onto allophane requiring both the narrow pores (voids formed by the primary nano-spherules) and the acid centres located at the defect surfaces of the primary spherules. The validity of this coupled mechanism for the sorption of organic matter was confirmed by the concomitant blocking of acid centres (129Xe NMR data) and the decrease of the N2-available pore volumes (Vmicro and Vmeso) in the model samples DOM/- and NOM/allophane (DOM = dissolved OM, NOM = natural OM). In the Andosol, the high resistance of SOM against oxidation (OCresist = 15-50%) was combined with preferential accumulation of certain organic compounds, e.g. potentially labile substrates such as carbohydrates, and the low molecular weight species such as amino acids. This feature was attributed to the peculiar microporous tortuous structure of allophane aggregates that likely impose certain criteria for the chemical nature and size of mineral-bound SOM. On the other hand, the revealed dominance of nanoparticulate Fe oxyhydroxides (57% ferrihydrite) and Fe-substituted allophane (supposedly formed due to co-precipitation of the Al, Si and Fe in the course of volcanic soil formation) may substantially contribute to the formation of highly resistant organo-mineral associations through the enhanced extent of reactive surface groups in nanoparticles, increased surface charge density and electron accepting properties of substituting Fe3+ species that supposedly enhance the proportion of oxidised organic components.

Use of UO 2 films for electrochemical studies

NASA Astrophysics Data System (ADS)

Miserque, F.; Gouder, T.; Wegen, D. H.; Bottomley, P. D. W.

2001-10-01

UO 2 films have been prepared by dc reactive sputtering of a uranium metal target in an Ar/O 2 atmosphere. We have used the films deposited on gold substrates as working electrodes for electrochemical investigations as simulating the surfaces of fuel pellets. Film composition was determined by photoelectron spectroscopy (XPS and UPS) and X-ray diffraction (XRD). The oxide stoichiometry as a function of deposition conditions was determined and the appropriate conditions for UO 2.0 formation established. AC impedance and cyclic voltammetry measurements were performed. A double RC electrical equivalent circuit was used to fit the data from impedance measurements, similar to those used in unirradiated UO 2 or spent fuel pellets. However due to the porosity or adhesion defects on the thin films that permitted a direct contact between the solution and the gold substrate, we were obliged to add a contribution simulating the water-gold system. Cyclic voltammetry measurements show the influence of pH on the dissolution mechanism. Alkaline solutions permit the formation of an oxidised layer (UO 2.33) which is not present in the acidic solutions. In both pH=2 and pH=6 solutions, a U VI species layer is formed.

Functionalization of graphene oxide nanostructures improves photoluminescence and facilitates their use as optical probes in preclinical imaging

NASA Astrophysics Data System (ADS)

Prabhakar, Neeraj; Näreoja, Tuomas; von Haartman, Eva; Şen Karaman, Didem; Burikov, Sergey A.; Dolenko, Tatiana A.; Deguchi, Takahiro; Mamaeva, Veronika; Hänninen, Pekka E.; Vlasov, Igor I.; Shenderova, Olga A.; Rosenholm, Jessica M.

2015-06-01

Recently reported photoluminescent nanographene oxides (nGOs), i.e. nanographene oxidised with a sulfuric/nitric acid mixture (SNOx method), have tuneable photoluminescence and are scalable, simple and fast to produce optical probes. This material belongs to the vast class of photoluminescent carbon nanostructures, including carbon dots, nanodiamonds (NDs), graphene quantum dots (GQDs), all of which demonstrate a variety of properties that are attractive for biomedical imaging such as low toxicity and stable photoluminescence. In this study, the nGOs were organically surface-modified with poly(ethylene glycol)-poly(ethylene imine) (PEG-PEI) copolymers tagged with folic acid as the affinity ligand for cancer cells expressing folate receptors. The functionalization enhanced both the cellular uptake and quantum efficiency of the photoluminescence as compared to non-modified nGOs. The nGOs exhibited an excitation dependent photoluminescence that facilitated their detection with a wide range of microscope configurations. The functionalized nGOs were non-toxic, they were retained in the stained cell population over a period of 8 days and they were distributed equally between daughter cells. We have evaluated their applicability in in vitro and in vivo (chicken embryo CAM) models to visualize and track migratory cancer cells. The good biocompatibility and easy detection of the functionalized nGOs suggest that they could address the limitations faced with quantum dots and organic fluorophores in long-term in vivo biomedical imaging.Recently reported photoluminescent nanographene oxides (nGOs), i.e. nanographene oxidised with a sulfuric/nitric acid mixture (SNOx method), have tuneable photoluminescence and are scalable, simple and fast to produce optical probes. This material belongs to the vast class of photoluminescent carbon nanostructures, including carbon dots, nanodiamonds (NDs), graphene quantum dots (GQDs), all of which demonstrate a variety of properties that are attractive for biomedical imaging such as low toxicity and stable photoluminescence. In this study, the nGOs were organically surface-modified with poly(ethylene glycol)-poly(ethylene imine) (PEG-PEI) copolymers tagged with folic acid as the affinity ligand for cancer cells expressing folate receptors. The functionalization enhanced both the cellular uptake and quantum efficiency of the photoluminescence as compared to non-modified nGOs. The nGOs exhibited an excitation dependent photoluminescence that facilitated their detection with a wide range of microscope configurations. The functionalized nGOs were non-toxic, they were retained in the stained cell population over a period of 8 days and they were distributed equally between daughter cells. We have evaluated their applicability in in vitro and in vivo (chicken embryo CAM) models to visualize and track migratory cancer cells. The good biocompatibility and easy detection of the functionalized nGOs suggest that they could address the limitations faced with quantum dots and organic fluorophores in long-term in vivo biomedical imaging. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr01403d

Comparative habitability of the Earth, Venus and Mars in the young solar system.

NASA Astrophysics Data System (ADS)

Nisbet, E. G.

2008-09-01

Abstract To be habitable, a planet must be suitable at all scales [1]. The setting in relation to the star must be right, so that surface temperatures can sustain liquid water. The planetary inventory must be suitable, providing surface water, rocks, and accessible thermodynamic disequilibrium. There must be physical habitat, especially mud and hydrothermal systems around volcanoes. Planets are not static: they evolve. Habitability must evolve with the planet. On accretion, the processes of impact and formation of volatile inventory must be suitable. Tectonics and volcanism must supply redox contrasts and biochemical substrates capable not only of starting life but of sustaining it. Mud or soft sediment may be essential: it is unlikely that early life can sustain itself in open water or air. This requirement for mud has tectonic implications. Once life starts, it immediately alters its own environment, by consuming nutrient. Until photosynthesis evolves, inorganic sources must supply sustained redox contrast to the local environment. But life changes its setting, both by risky alterations to the atmospheric greenhouse (drawing down CO2, emitting CH4), and by partitioning reductants (e.g. as dead bodies) and oxidants (waste). Somehow the planet must avoid both freezing and boiling. Early in the history of the solar system, a passing galactic tourist might have rated Venus as the likeliest habitat for life, Mars next, and Earth last of the three. Venus was warm and hospitable, Mars clement, and Earth had been though an impact episode powerful enough to make a silicate atmosphere. By comparison with Earth there are many potential environmental settings on Mars in which life may once have occurred, or may even continue to exist. Perhaps Mars seeded earth? Yet today the reverse order of habitability is the case. Earth today is safeguarded by a reworked atmosphere that is 99% of biological construction, maintained in active disequilibrium with the surface. Mars, in contrast, is chilly oxidised permafrost where kinetics alone would make life difficult. Venus has achieved sustainable equilibrium, where equilibrium, being the opposite of life, equals death. Geologically, how and why did this happen? Earth was not necessarily the Goldilocks planet, neither too warm not too cold. But it did have a degree of locally-accessible disequilibrium, to sustain early life. Life itself, especially the enzyme rubisco, that mediates carbon transfer from air to organism, then actively managed to rework the surface of Earth. From the moment life began, it remade its house to maintain habitability. Life, if ever present on Mars, may have simply died from lack of resources. Any life on Venus would have died of dehydration or by being cooked. However, terraforming may now be worth attempting on both planets: as on Earth it may be self-sustaining, even after the terraforming species becomes extinct. [1] Nisbet, E.G. Zahnle, K., Gersimov, M., Helbert, J., Jaumann, R., Hofmann, B., Benzerara, K, Westall, F., Spc. Sci. Rev. (2007), 129, 79-121.

Effect of glutathione aerosol on oxidant-antioxidant imbalance in idiopathic pulmonary fibrosis.

PubMed

Borok, Z; Buhl, R; Grimes, G J; Bokser, A D; Hubbard, R C; Holroyd, K J; Roum, J H; Czerski, D B; Cantin, A M; Crystal, R G

1991-07-27

Idiopathic pulmonary fibrosis (IPF) is characterised by alveolar inflammation, exaggerated release of oxidants, and subnormal concentrations of the antioxidant glutathione in respiratory epithelial lining fluid (ELF). Glutathione (600 mg twice daily for 3 days) was given by aerosol to 10 patients with IPF. Total ELF glutathione rose transiently, ELF oxidised glutathione concentrations increased, and there was a decrease in spontaneous superoxide anion release by alveolar macrophages. Thus, glutathione by aerosol could be a means of reversing the oxidant-antioxidant imbalance in IPF.

The Electronic Spectra of Phthalocyanine Radical Anions and Cations.

DTIC Science & Technology

1985-03-01

415. (10) McHugh , A.J., Gouterman, M., Weiss, J., Theoret. Chim. Acta, 1972, 24, 346. (11) Henriksson, A. and Sundbom, M., Theoret. Chim. Acta, 1972, 27...oxidisable. The spectra for the nickel (II) Pc species exactly parallel the main group data since no change in oxidation state of the nickel ion is expect- ed18...and no charge transfer is expected in the region under study. 6 In summary, the main group complexes, nickel and cobalt species all have parallel

Rapid estimation of the oxidative activities of individual phenolics in crude plant extracts.

PubMed

Vihakas, Matti; Pälijärvi, Maija; Karonen, Maarit; Roininen, Heikki; Salminen, Juha-Pekka

2014-07-01

Previous studies of purified phenolic compounds have revealed that some phenolics, especially ellagitannins, can autoxidise under alkaline conditions, which predominate in the midgut of lepidopteran larvae. To facilitate screening for the pro-oxidant activities of all types of phenolic compounds from crude plant extracts, we developed a method that combined our recent spectrophotometric bioactivity method with an additional chromatographic step via UPLC-DAD-MS. This method allowed us to estimate the total pro-oxidant capacities of crude extracts from 12 plant species and to identify the individual phenolic compounds that were responsible for the detected activities. It was found that the pro-oxidant capacities of the plant species (i.e., the concentrations of the easily-oxidised phenolics) varied from 0 to 57 mg/g dry wt, representing from 0% to 46% of the total phenolics from different species. UPLC-DAD-MS analysis revealed that most flavonol and flavone glycosides were only slightly affected by alkaline conditions, thus indicating their low pro-oxidant activity. Interestingly, myricetin-type compounds differed from the other flavonoids, as their concentrations decreased strongly due to alkaline incubation. The same effect was detected for hydrolysable tannins and prodelphinidins, suggesting that a pyrogallol sub-structure could be a key structural component that partially explains their easy oxidation at high pH. Other types of phenolic compounds, such as hydroxycinnamic acids, were relatively active, as well. These findings demonstrate that this method displays the potential to identify most of the active and inactive pro-oxidant phenolic compounds in various plant species. Copyright © 2014 Elsevier Ltd. All rights reserved.

Flavonoids from acai (Euterpe oleracea Mart.) pulp and their antioxidant and anti-inflammatory activities.

PubMed

Kang, Jie; Xie, Chenghui; Li, Zhimin; Nagarajan, Shanmugam; Schauss, Alexander G; Wu, Tong; Wu, Xianli

2011-09-01

Five flavonoids, (2S,3S)-dihyrokaempferol 3-O-β-d-glucoside (1) and its isomer (2R,3R)-dihydrokaempferol 3-O-β-d-glucoside (2) , isovitexin (3), velutin (4) and 5,4'-dihydroxy-7,3',5'-trimethoxyflavone (5), were isolated from acai (Euterpe oleracea Mart.) pulp. The structures of these compounds were elucidated based upon spectroscopic and chemical analyses. To our knowledge, compounds 1, 2, 4 and 5 were identified from acai pulp for the first time. The in vitro antioxidant activities of these compounds were evaluated by the oxygen radial absorbance capacity (ORAC) assay. The ORAC values varied distinctly (4458.0-22404.5μmol Trolox equivalent (TE)/g) from 5,4'-dihydroxy-7,3',5'-trimethoxyflavone (5) to isovitexin (3) and were affected by the numbers/positions of hydroxyl groups, substitute groups, as well as stereo configuration. The anti-inflammatory effects of these compounds were screened by the secreted embryonic alkaline phosphatase (SEAP) reporter assay, which is designed to measure NF-κB activation. Velutin (4) was found to dose-dependently inhibit SEAP secretion in RAW-blue cells induced by LPS, with an IC50 value of 2.0μM. Velutin (4) also inhibited SEAP secretion induced by oxidised LDL, indicating potential athero-protective effects. Copyright © 2011 Elsevier Ltd. All rights reserved.

Conformational properties of serine proteinase inhibitors (serpins) confer multiple pathophysiological roles.

PubMed

Janciauskiene, S

2001-03-26

Serine proteinase inhibitors (Serpins) are irreversible suicide inhibitors of proteases that regulate diverse physiological processes such as coagulation, fibrinolysis, complement activation, angiogenesis, apoptosis, inflammation, neoplasia and viral pathogenesis. The molecular structure and physical properties of serpins permit these proteins to adopt a number of variant conformations under physiological conditions including the native inhibitory form and several inactive, non-inhibitory forms, such as complexes with protease or other ligands, cleaved, polymerised and oxidised. Alterations of a serpin which affect its structure and/or secretion and thus reduce its functional levels may result in pathology. Serpin dysfunction has been implicated in thrombosis, emphysema, liver cirrhosis, immune hypersensitivity and mental disorders. The loss of inhibitory activity of serpins necessarily results in an imbalance between proteases and their inhibitors, but it may also have other physiological effects through the generation of abnormal concentrations of modified, non-inhibitory forms of serpins. Although these forms of inhibitory serpins are detected in tissues and fluids recovered from inflammatory sites, the important questions of which conditions result in generation of different molecular forms of serpins, what biological function these forms have, and which of them are directly linked to pathologies and/or may be useful markers for characterisation of disease states, remain to be answered. Elucidation of the biological activities of non-inhibitory forms of serpins may provide useful insights into the pathogenesis of diseases and suggest new therapeutic strategies.

Modulation of the antioxidative response of Spartina densiflora against iron exposure.

PubMed

Martínez Domínguez, David; Torronteras Santiago, Rafael; Córdoba García, Francisco

2009-06-01

Spartina densiflora, an invader cordgrass living in polluted salt marshes of the Odiel estuary (SW Spain), was collected and cultured under controlled laboratory conditions. After acclimation to non-polluted soils for 28 days, both metabolites and enzymes activities used as indicators of oxidative stress were reduced significantly. Then, plants were exposed to 500 and 1000 ppm Fe-ethylenediamine-N,N'-2-hydroxyphenyl acetic acid (EDDHA) for 28 days. Our data demonstrate that iron content in leaves was enhanced by iron exposure. This iron increase caused an enhancement in the concentration of H2O2, hydroperoxides and lipid peroxidation, and a decrease in chlorophyll levels. Thus, iron exposure led to oxidative stress conditions. However, oxidative indicators stabilised after first 2 weeks of exposure, although the highest iron levels in leaves were reached at the end of treatments. Iron exposure induced an enhancement of catalase, ascorbate peroxidase and guaiacol peroxidase activities, together with an increase in total and oxidised ascorbate. This response may be defensive against oxidative stress and thus help to explain why cell oxidative damages were stabilised. Thus, by using a sensitive long-time protocol, iron-dependent oxidative damages may be controlled and even reverted successfully by the activation of the antioxidative defences of S. densiflora. This efficient antioxidative system, rapidly modulated in response to excess iron and other environmental stressors, may account for S. densiflora's successful adaptation to stress conditions in its habitat.

Validation of protein carbonyl measurement: A multi-centre study

PubMed Central

Augustyniak, Edyta; Adam, Aisha; Wojdyla, Katarzyna; Rogowska-Wrzesinska, Adelina; Willetts, Rachel; Korkmaz, Ayhan; Atalay, Mustafa; Weber, Daniela; Grune, Tilman; Borsa, Claudia; Gradinaru, Daniela; Chand Bollineni, Ravi; Fedorova, Maria; Griffiths, Helen R.

2014-01-01

Protein carbonyls are widely analysed as a measure of protein oxidation. Several different methods exist for their determination. A previous study had described orders of magnitude variance that existed when protein carbonyls were analysed in a single laboratory by ELISA using different commercial kits. We have further explored the potential causes of variance in carbonyl analysis in a ring study. A soluble protein fraction was prepared from rat liver and exposed to 0, 5 and 15 min of UV irradiation. Lyophilised preparations were distributed to six different laboratories that routinely undertook protein carbonyl analysis across Europe. ELISA and Western blotting techniques detected an increase in protein carbonyl formation between 0 and 5 min of UV irradiation irrespective of method used. After irradiation for 15 min, less oxidation was detected by half of the laboratories than after 5 min irradiation. Three of the four ELISA carbonyl results fell within 95% confidence intervals. Likely errors in calculating absolute carbonyl values may be attributed to differences in standardisation. Out of up to 88 proteins identified as containing carbonyl groups after tryptic cleavage of irradiated and control liver proteins, only seven were common in all three liver preparations. Lysine and arginine residues modified by carbonyls are likely to be resistant to tryptic proteolysis. Use of a cocktail of proteases may increase the recovery of oxidised peptides. In conclusion, standardisation is critical for carbonyl analysis and heavily oxidised proteins may not be effectively analysed by any existing technique. PMID:25560243

The critical micelle concentration of lecithin in bulk oils and medium chain triacylglycerol is influenced by moisture content and total polar materials.

PubMed

Kim, JiSu; Kim, Mi-Ja; Lee, JaeHwan

2018-09-30

Effects of different moisture contents and oxidised compounds on the critical micelle concentration (CMC) of lecithin were determined in bulk oils and in medium-chain triacylglycerols (MCT). CMC of lecithin in MCT was significantly higher than that in other vegetable oils including olive, soybean, corn, and rapeseed oils (p < 0.05). Presence of moisture significantly affected the CMC of lecithin in MCT (p < 0.05). CMC of lecithin was high when the moisture content was below 900 ppm, whereas at a moisture content of 1000 ppm, CMC of lecithin decreased significantly (p < 0.05), and then started to increase. Addition of total polar materials (TPM), which are oxidation products, at 3 and 5% concentrations, decreased CMC of lecithin significantly (p < 0.05) in MCT, compared to when 0, 1, and 1.5% of TPM was added to MCT. As the degree of oxidation increased in corn oil, CMC of lecithin gradually decreased. Additionally, under different moisture contents, corn oils showed a similar pattern of CMC of lecithin in MCT, whereas oxidised corn oil had a little lower CMC of lecithin than unoxidised corn oil. The results clearly showed that the concentration of lecithin for the formation of micelles is greatly influenced by the presence of oxidation products and the moisture content in bulk oils. Copyright © 2018 Elsevier Ltd. All rights reserved.

Enzymatic oxidation of 2-phenylethylamine to phenylacetic acid and 2-phenylethanol with special reference to the metabolism of its intermediate phenylacetaldehyde.

PubMed

Panoutsopoulos, Georgios I; Kouretas, Demetrios; Gounaris, Elias G; Beedham, Christine

2004-12-01

2-phenylethylamine is an endogenous constituent of the human brain and is implicated in cerebral transmission. This bioactive amine is also present in certain foodstuffs such as chocolate, cheese and wine and may cause undesirable side effects in susceptible individuals. Metabolism of 2-phenylethylamine to phenylacetaldehyde is catalysed by monoamine oxidase B but the oxidation to its acid is usually ascribed to aldehyde dehydrogenase and the contribution of aldehyde oxidase and xanthine oxidase, if any, is ignored. The objective of this study was to elucidate the role of the molybdenum hydroxylases, aldehyde oxidase and xanthine oxidase, in the metabolism of phenylacetaldehyde derived from its parent biogenic amine. Treatments of 2-phenylethylamine with monoamine oxidase were carried out for the production of phenylacetaldehyde, as well as treatments of synthetic or enzymatic-generated phenylacetaldehyde with aldehyde oxidase, xanthine oxidase and aldehyde dehydrogenase. The results indicated that phenylacetaldehyde is metabolised mainly to phenylacetic acid with lower concentrations of 2-phenylethanol by all three oxidising enzymes. Aldehyde dehydrogenase was the predominant enzyme involved in phenylacetaldehyde oxidation and thus it has a major role in 2-phenylethylamine metabolism with aldehyde oxidase playing a less prominent role. Xanthine oxidase does not contribute to the oxidation of phenylacetaldehyde due to low amounts being present in guinea pig. Thus aldehyde dehydrogenase is not the only enzyme oxidising xenobiotic and endobiotic aldehydes and the role of aldehyde oxidase in such reactions should not be ignored.

Voltammetric determination of arsenic in high iron and manganese groundwaters.

PubMed

Gibbon-Walsh, Kristoff; Salaün, Pascal; Uroic, M Kalle; Feldmann, Joerg; McArthur, John M; van den Berg, Constant M G

2011-09-15

Determination of the speciation of arsenic in groundwaters, using cathodic stripping voltammetry (CSV), is severely hampered by high levels of iron and manganese. Experiments showed that the interference is eliminated by addition of EDTA, making it possible to determine the arsenic speciation on-site by CSV. This work presents the CSV method to determine As(III) in high-iron or -manganese groundwaters in the field with only minor sample treatment. The method was field-tested in West-Bengal (India) on a series of groundwater samples. Total arsenic was subsequently determined after acidification to pH 1 by anodic stripping voltammetry (ASV). Comparative measurements by ICP-MS as reference method for total As, and by HPLC for its speciation, were used to corroborate the field data in stored samples. Most of the arsenic (78±0.02%) was found to occur as inorganic As(III) in the freshly collected waters, in accordance with previous studies. The data shows that the modified on-site CSV method for As(III) is a good measure of water contamination with As. The EDTA was also found to be effective in stabilising the arsenic speciation for longterm sample storage at room temperature. Without sample preservation, in water exposed to air and sunlight, the As(III) was found to become oxidised to As(V), and Fe(II) oxidised to Fe(III), removing the As(V) by adsorption on precipitating Fe(III)-hydroxides within a few hours. Copyright © 2011 Elsevier B.V. All rights reserved.

Redox, iron, and nutritional status of children during swimming training.

PubMed

Kabasakalis, Athanasios; Kalitsis, Konstantinos; Nikolaidis, Michalis G; Tsalis, George; Kouretas, Dimitris; Loupos, Dimitris; Mougios, Vassilis

2009-11-01

Effects of exercise training on important determinants of children's long-term health, such as redox and iron status, have not been adequately investigated. The aim of the present study was to examine changes in markers of the redox, iron and nutritional status of boy and girl swimmers during a prolonged period of training. 11 boys and 13 girls, aged 10-11 years, were members of a swimming club. They were assessed at the beginning of the training season, at 13 weeks and at 23 weeks through blood sampling and recording of the diet. Reduced glutathione increased at 13 and 23 weeks, whereas oxidised glutathione decreased at 13 weeks, resulting in an increase of the reduced/oxidised glutathione ratio at 13 and 23 weeks. Total antioxidant capacity, catalase, thiobarbituric acid-reactive substances, hemoglobin, transferrin saturation and ferritin did not change significantly. Carbohydrate intake was below 50% of energy and fat intake was above 40% of energy. Intakes of saturated fatty acids and cholesterol were excessive. Iron intake was adequate but intakes of folate, vitamin E, calcium and magnesium did not meet the recommended daily allowances. No significant differences were found between sexes in any of the parameters measured. In conclusion, child swimmers improved the redox status of glutathione during training, although the intake of antioxidant nutrients did not change. The iron status was not impaired by training. Suboptimal intake of several nutrients suggests the need for nutritional monitoring and education of children athletes.

Changes in chemical composition and antioxidative properties of rye ginger cakes during their shelf-life.

PubMed

Zieliński, Henryk; del Castillo, Maria Dolores; Przygodzka, Małgorzata; Ciesarova, Zuzana; Kukurova, Kristina; Zielińska, Danuta

2012-12-15

Changes in chemical composition and antioxidative properties of rye ginger cakes during their shelf-life were investigated in this study. In particular, the changes in antioxidants content, antioxidative and reducing capacity, and Maillard reaction development in rye ginger cakes after long-term storage were addressed. Ginger cakes produced according to the traditional and current recipe were stored for 5 years at room temperature in a dark place. The total phenolic compounds (TPC), inositol hexaphosphate (IP6), reduced (GSH) and oxidised glutathione (GSSG) contents, antioxidant and reducing capacity and Maillard reaction products (MRPs) were determined in ginger cakes after storage and then compared to those measured after baking. After long-term storage a decrease in TPC and IP6 contents in cakes was noted. In contrast, an increase in antioxidative and reducing capacity of stored cakes was observed. Long-term storage induced formation of furosine, advanced and final Maillard reaction products and caused changes in both reduced and oxidised forms of glutathione. After long-term storage the modest changes in furosine, FAST index and browning in ginger cake formulated with dark rye flour may suggest that this product is the healthiest among others. Therefore, traditional rye ginger cakes can be considered as an example of a healthy food that is also relatively stable during long term storage as noted by the small chemical changes observed in its composition. Copyright © 2012 Elsevier Ltd. All rights reserved.

Antioxidant effect of naturally occurring xanthines on the oxidative damage of DNA bases

NASA Astrophysics Data System (ADS)

Vieira, A. J. S. C.; Telo, J. P.; Pereira, H. F.; Patrocínio, P. F.; Dias, R. M. B.

1999-01-01

The repair of the oxidised radicals of adenine and guanosine by several naturally occurring xanthines was studied. Each pair of DNA purine/xanthine was made to react with the sulphate radical and the decrease of the concentration of both compounds was measured by HPLC as a function of irradiation time. The results show that xanthine efficiently prevents the oxidation of the two DNA purines. Theophyline and paraxanthine repair the oxidised radical of adenine but not the one from guanosine. Theobromine and caffeine do not show any protecting effect. An order of the oxidation potentials of all the purines studied is proposed. La réparation des radicaux oxydés de l'adénine et de la guanosine par des xanthines naturelles a été étudiée en soumettant chaque paire base de l'ADN/xanthine à l'oxydation par le radical sulfate et en mesurant par HPLC la disparition des deux composés en fonction du temps d'irradiation. Les résultats montrent que la xanthine joue un rôle protecteur efficace contre l'oxydation des deux purines de l'ADN. La théophyline et la paraxanthine réparent le radical oxydé de l'adénine mais pas celui de la guanosine. La théobromine et la cafeíne n'ont pas d'effet protecteur. Un ordre de potentiels d'oxydation des purines étudiées est proposé.

Triglycerides and small dense low density lipoprotein in the discrimination of coronary heart disease risk in South Asian populations.

PubMed

Patel, J V; Caslake, M J; Vyas, A; Cruickshank, J K; Prabhakaran, D; Bhatnagar, D; Reddy, K S; Lip, G Y H; Mackness, M I; Hughes, E A; Durrington, P N

2010-04-01

Coronary heart disease (CHD) is exceptionally prevalent amongst globally dispersed migrant groups originating from the Indian subcontinent, but the contribution of dyslipidaemia to their increased risk remains poorly defined. Fasting lipids and lipoproteins, apolipoproteins (Apo), low density lipoprotein (LDL) diameter and oxidised LDL were measured amongst rural Indians in India (n=294) and their migrant contemporaries in the UK (n=242). The performance of qualitative and quantitative measures of lipid metabolism were compared in the discrimination of WHO defined metabolic risk and raised Framingham CHD risk scores (>15%) using Receiver Operating Characteristic (ROC) curves. LDL diameter was correlated with triglycerides (R(2)=0.12, P<0.001) and with high density lipoprotein (HDL) cholesterol levels (R(2)=0.15, P<0.001) in both groups. Migrants had less small dense LDL (95% CI: 12.5-14.2%) vs. rural Indians (15.7-17.2, P<0.05). On ROC analysis, triglycerides were the only consistent discriminators of metabolic and CHD risk scores (all P< or =0.001). Apo B was also a strong indicator of raised CHD risk scores. Irrespective of site, individuals with raised triglycerides also had higher total cholesterol and Apo B, denser LDL, lower HDL and more oxidised LDL (all P< or =0.01). Fasting triglycerides reflect both qualitative and quantitative aspects of lipid metabolism, and are a comprehensive discriminator of CHD risk in this South Asian population. Crown Copyright 2009. Published by Elsevier Ireland Ltd. All rights reserved.

Analysis of oxidised heavy paraffininc products by high temperature comprehensive two-dimensional gas chromatography.

PubMed

Potgieter, H; Bekker, R; Beigley, J; Rohwer, E

2017-08-04

Heavy petroleum fractions are produced during crude and synthetic crude oil refining processes and they need to be upgraded to useable products to increase their market value. Usually these fractions are upgraded to fuel products by hydrocracking, hydroisomerization and hydrogenation processes. These fractions are also upgraded to other high value commercial products like lubricant oils and waxes by distillation, hydrogenation, and oxidation and/or blending. Oxidation of hydrogenated heavy paraffinic fractions produces high value products that contain a variety of oxygenates and the characterization of these heavy oxygenates is very important for the control of oxidation processes. Traditionally titrimetric procedures are used to monitor oxygenate formation, however, these titrimetric procedures are tedious and lack selectivity toward specific oxygenate classes in complex matrices. Comprehensive two-dimensional gas chromatography (GC×GC) is a way of increasing peak capacity for the comprehensive analysis of complex samples. Other groups have used HT-GC×GC to extend the carbon number range attainable by GC×GC and have optimised HT-GC×GC parameters for the separation of aromatics, nitrogen-containing compounds as well as sulphur-containing compounds in heavy petroleum fractions. HT-GC×GC column combinations for the separation of oxygenates in oxidised heavy paraffinic fractions are optimised in this study. The advantages of the HT-GC×GC method in the monitoring of the oxidation reactions of heavy paraffinic fraction samples are illustrated. Copyright © 2017 Elsevier B.V. All rights reserved.

Enhancing thermoelectrochemical properties by tethering ferrocene to the anion or cation of ionic liquids: altered thermodynamics and solubility.

PubMed

Aldous, Leigh; Black, Jeffrey J; Elias, Maximo C; Gélinas, Bruno; Rochefort, Dominic

2017-09-13

Entropic changes inherent within a redox process typically result in significant temperature sensitivity. This can be utilised positively or can be a detrimental process. This study has investigated the thermoelectrochemical properties (temperature-dependant electrochemistry) of the ferrocenium|ferrocene redox couple in an ionic liquid, and in particular the effect of covalently tethering this redox couple to fixed positive or negative charges. As such, the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide was employed to dissolve ferrocene, as well as cationic-tethered ferrocene (the 1-ethyl-3-(methylferrocenyl)imidazolium cation) and anionic-tethered ferrocene (the ferrocenylsulfonyl(trifluoromethylsulfonyl)imide anion). These systems were characterised in terms of their voltammetry (apparent formal potentials, diffusion coefficients and electron transfer rate constants) and thermoelectrochemistry (temperature coefficients of the cell potential or 'Seebeck coefficients', short circuit current densities and power density outputs). The oxidised cationic species behaved like a dicationic species and was thus 6-fold more effective at converting waste thermal energy to electrical power within a thermoelectrochemical cell than unmodified ferrocene. This was almost exclusively due to a significant boost in the Seebeck coefficient of this redox couple. Conversely, the oxidised anionic species was formally a zwitterion, but this zwitterionic species behaved thermodynamically like a neutral species. The inverted entropic change upon going from ferrocene to anion-tethered ferrocene allowed development of a largely temperature-insensitive reference potential based upon a mixture of acetylferrocene and ferricenyl(iii)sulfonyl(trifluoromethylsulfonyl)imide.

Synergistic effect of biogenic Fe3+ coupled to S° oxidation on simultaneous bioleaching of Cu, Co, Zn and As from hazardous Pyrite Ash Waste.

PubMed

Panda, Sandeep; Akcil, Ata; Mishra, Srabani; Erust, Ceren

2017-03-05

Pyrite ash, a waste by-product formed during roasting of pyrite ores, is a good source of valuable metals. The waste is associated with several environmental issues due to its dumping in sea and/or land filling. Although several other management practices are available for its utilization, the waste still awaits and calls for an eco-friendly biotechnological application for metal recovery. In the present study, chemolithotrophic meso-acidophilic iron and sulphur oxidisers were evaluated for the first time towards simultaneous mutli-metal recovery from pyrite ash. XRD and XRF analysis indicated higher amount of Hematite (Fe 2 O 3 ) in the sample. ICP-OES analysis indicated concentrations of Cu>Zn>Co>As that were considered for bioleaching. Optimization studies indicated Cu - 95%, Co - 97%, Zn - 78% and As - 60% recovery within 8days at 10% pulp density, pH - 1.75, 10% (v/v) inoculum and 9g/L Fe 2+ . The productivity of the bioleaching system was found to be Cu - 1696ppm/d (12% dissolution/d), Co - 338ppm/d (12.2% dissolution/d), Zn k 576ppm/d (9.8% dissolution/d) and As - 75ppm/d (7.5% dissolution/d). Synergistic actions for Fe 2+ - S° oxidation by iron and sulphur oxidisers were identified as the key drivers for enhanced metal dissolution from pyrite ash sample. Copyright © 2016 Elsevier B.V. All rights reserved.

Encapsulation of the heteroepitaxial growth of wide band gap γ-CuCl on silicon substrates

NASA Astrophysics Data System (ADS)

Lucas, F. O.; O'Reilly, L.; Natarajan, G.; McNally, P. J.; Daniels, S.; Taylor, D. M.; William, S.; Cameron, D. C.; Bradley, A. L.; Miltra, A.

2006-01-01

γ-CuCl semiconductor material has been identified as a candidate material for the fabrication of blue-UV optoelectronic devices on Si substrates due to its outstanding electronic, lattice and optical properties. However, CuCl thin films oxidise completely into oxyhalides of Cu II within a few days of exposure to air. Conventional encapsulation of thin γ-CuCl by sealed glass at a deposition/curing temperature greater than 250 °C cannot be used because CuCl interacts chemically with Si substrates when heated above that temperature. In this study we have investigated the behaviour of three candidate dielectric materials for use as protective layers for the heteroepitaxial growth of γ-CuCl on Si substrates: SiO 2 deposited by plasma-enhanced chemical vapour deposition (PECVD), organic polysilsesquioxane-based spin on glass material (PSSQ) and cyclo olefin copolymer (COC) thermoplastic-based material. The optical properties (UV/Vis and IR) of the capped luminescent CuCl films were studied as a function of time, up to 28 days and compared with bare uncapped films. The results clearly show the efficiency of the protective layers. Both COC and the PSSQ layer prevented CuCl film from oxidising while SiO 2 delayed the effect of oxidation. The dielectric constant of the three protective layers was evaluated at 1 MHz to be 2.3, 3.6 and 6.9 for C0C, SiO 2 and PSSQ, respectively.

Hypoxic pulmonary vasoconstriction in the absence of pretone: essential role for intracellular Ca2+ release

PubMed Central

Connolly, Michelle J; Prieto-Lloret, Jesus; Becker, Silke; Ward, Jeremy P T; Aaronson, Philip I

2013-01-01

Hypoxic pulmonary vasoconstriction (HPV) maintains blood oxygenation during acute hypoxia but contributes to pulmonary hypertension during chronic hypoxia. The mechanisms of HPV remain controversial, in part because HPV is usually studied in the presence of agonist-induced preconstriction (‘pretone’). This potentiates HPV but may obscure and distort its underlying mechanisms. We therefore carried out an extensive assessment of proposed mechanisms contributing to HPV in isolated intrapulmonary arteries (IPAs) in the absence of pretone by using a conventional small vessel myograph. Hypoxia elicited a biphasic constriction consisting of a small transient (phase 1) superimposed upon a sustained (phase 2) component. Neither phase was affected by the L-type Ca2+ channel antagonists diltiazem (10 and 30 μm) or nifedipine (3 μm). Application of the store-operated Ca2+ entry (SOCE) blockers BTP2 (10 μm) or SKF96365 (50 μm) attenuated phase 2 but not phase 1, whereas a lengthy (30 min) incubation in Ca2+-free physiological saline solution similarly reduced phase 2 but abolished phase 1. No further effect of inhibition of HPV was observed if the sarco/endoplasmic reticulum Ca2+-ATPase inhibitor cyclopiazonic acid (30 μm) was also applied during the 30 min incubation in Ca2+-free physiological saline solution. Pretreatment with 10 μm ryanodine and 15 mm caffeine abolished both phases, whereas treatment with 100 μm ryanodine attenuated both phases. The two-pore channel blocker NED-19 (1 μm) and the nicotinic acid adenine dinucleotide phosphate (NAADP) antagonist BZ194 (200 μm) had no effect on either phase of HPV. The lysosomal Ca2+-depleting agent concanamycin (1 μm) enhanced HPV if applied during hypoxia, but had no effect on HPV during a subsequent hypoxic challenge. The cyclic ADP ribose antagonist 8-bromo-cyclic ADP ribose (30 μm) had no effect on either phase of HPV. Neither the Ca2+-sensing receptor (CaSR) blocker NPS2390 (0.1 and 10 μm) nor FK506 (10 μm), a drug which displaces FKBP12.6 from ryanodine receptor 2 (RyR2), had any effect on HPV. HPV was virtually abolished by the rho kinase blocker Y-27632 (1 μm) and attenuated by the protein kinase C inhibitor Gö6983 (3 μm). Hypoxia for 45 min caused a significant increase in the ratio of oxidised to reduced glutathione (GSSG/GSH). HPV was unaffected by the NADPH oxidase inhibitor VAS2870 (10 μm), whereas phase 2 was inhibited but phase 1 was unaffected by the antioxidants ebselen (100 μm) and TEMPOL (3 mm). We conclude that both phases of HPV in this model are mainly dependent on [Ca2+]i release from the sarcoplasmic reticulum. Neither phase of HPV requires voltage-gated Ca2+ entry, but SOCE contributes to phase 2. We can detect no requirement for cyclic ADP ribose, NAADP-dependent lysosomal Ca2+ release, activation of the CaSR, or displacement of FKBP12.6 from RyR2 for either phase of HPV. Sustained HPV is associated with an oxidising shift in the GSSG/GSH redox potential and is inhibited by the antioxidants ebselen and TEMPOL, consistent with the concept that it requires an oxidising shift in the cell redox state or the generation of reactive oxygen species. PMID:23774281

Vitamin C and fibre consumption from fruits and vegetables improves oxidative stress markers in healthy young adults.

PubMed

Hermsdorff, Helen Hermana M; Barbosa, Kiriaque B F; Volp, Ana Carolina P; Puchau, Blanca; Bressan, Josefina; Zulet, M Ángeles; Martínez, J Alfredo

2012-04-01

The aim of the present cross-sectional study was to assess the potential relationships between fruit and vegetable (FV) consumption and some oxidative stress markers in young adults, with particular emphasis on fibre and vitamin C intake. The study enrolled 246 healthy subjects (eighty-eight men and 158 women), with a mean age of 22 (sd 3) years and a mean BMI of 21·9 (sd 2·8) kg/m2. Dietary intake, anthropometry, blood pressure, lifestyle features and blood biochemical data were assessed with validated procedures. Those subjects in the highest tertile (T) of FV consumption ( ≥ 705 g/d) had statistically lower oxidised LDL (ox-LDL) concentrations as well as higher plasma total antioxidant capacity (TAC) and glutathione peroxidase (GPx) activity (P for trend <0·05), after adjusting for sex, age, energy intake, physical activity, smoking, BMI, vitamin supplement use and other confounding factors. Moreover, plasma ox-LDL concentrations showed a decreasing trend and TAC an increasing trend across tertiles of fibre (T3: ≥14 g/d) and vitamin C (T3: ≥150 mg/d) from FV intake, while GPx activity was positively associated with vitamin C intake (P for trend < 0·05). In conclusion, greater FV consumption was independently associated with reduced ox-LDL as well as increased TAC and GPx activity in healthy young adults, with dietary fibre and vitamin C from FV clearly being implicated in this beneficial relationship.

The redox budget of crust-derived fluid phases at the slab-mantle interface

NASA Astrophysics Data System (ADS)

Malaspina, N.; Langenhorst, F.; Tumiati, S.; Campione, M.; Frezzotti, M. L.; Poli, S.

2017-07-01

The redox processes taking place in the portion of the mantle on top of the subducting slab are poorly investigated and the redox potential of crust-derived fluid phases is still poorly constrained. A case study of supra-subduction mantle affected by metasomatism from crust-derived fluid phases is represented by garnet orthopyroxenites from the Maowu Ultramafic Complex (China) deriving from harzburgite precursors metasomatised at ∼4 GPa, 750-800 °C by a silica- and incompatible trace element-rich fluid phase. This metasomatism produced poikilitic orthopyroxene and inclusion-rich garnet porphyroblasts. Solid multiphase primary micro-inclusions in garnet display negative crystal shapes and infilling minerals (spinel, ±orthopyroxene, amphiboles, chlorite, ±talc, ±mica) occur with constant modal proportions, indicating that they derive from trapped solute-rich aqueous fluids. FT-IR hyper spectral imaging analyses and Raman spectroscopy, together with X-ray microtomography performed on single inclusions indicate that liquid water is still preserved at least in some inclusions (±spinel). To investigate the redox budget of these fluid phases, we measured for the first time the Fe3+ concentration of the micron-sized precipitates of the multiphase inclusions using EELS on a TEM. Results indicate that spinel contains up to 12% of Fe3+ with respect to the total iron, amphibole about 30%, while the ratio in inclusion phases such as chlorite and phlogopite may reach 70%. The Fe3+ fraction of the host garnet is equal to that measured in spinel as also confirmed by Flank Method EPMA measurements. Forward modelling fO2 calculations indicate that the garnet orthopyroxenites record ΔFMQ = -1.8 ÷ -1.5, therefore resulting apparently more reduced with respect to metasomatised supra-subduction garnet-peridotites. On the other hand, oxygen mass balance, performed both on the Maowu hybrid orthopyroxenite and on metasomatised supra-subduction garnet peridotites, indicate that the excess of oxygen (nO2) is the same (10 mol m-3). The oxygen mass balance of the crust-derived fluids (multiphase inclusions) also indicates that the fluid precipitates are more oxidised than the host rock, reaching up to 400 mol m-3 of nO2. This suggests that even after their interaction with the metasomatic orthopyroxenites, the residual fluid phases could be potentially carrier of oxidised components when it escapes the slab-mantle interface. Because of this gradient in nO2, a metasomatic front develops from the oxidised slab to the overlying lithospheric mantle wedge passing through a transitional layer of hybrid rocks at the slab-mantle interface.

X-PEEM, XPS and ToF-SIMS characterisation of xanthate induced chalcopyrite flotation: Effect of pulp potential

NASA Astrophysics Data System (ADS)

Kalegowda, Yogesh; Chan, Yuet-Loy; Wei, Der-Hsin; Harmer, Sarah L.

2015-05-01

Synchrotron-based X-ray photoemission electron microscopy (X-PEEM), X-ray photo-electron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and ultraviolet visible spectroscopy were used to characterize the flotation behaviour of chalcopyrite with xanthate at different processing conditions. The flotation recovery of chalcopyrite decreased from 97% under oxidative conditions (Eh ~ 385 mV SHE, pH 4) to 41% at a reductive potential of - 100 mV SHE (at pH 9). X-PEEM images constructed from the metal L3 absorption edges were used to produce near-edge X-ray absorption fine structure (NEXAFS) spectra from regions of interest, allowing the variability in mineral surface chemistry of each mineral particle to be analysed, and the effect of pulp potential (Eh) on the flotation of chalcopyrite to be determined. XPS, ToF-SIMS and NEXAFS analyses of chalcopyrite particles at oxidative conditions show that the surface was mildly oxidised and covered with adsorbed molecular CuEX. The Cu 2p XPS and Cu L2,3 NEXAFS spectra were dominated by CuI species attributed to bulk chalcopyrite and adsorbed CuEX. At a reductive potential of - 100 mV SHE, an increase in concentration of CuI and FeIII oxides and hydroxides was observed. X-PEEM analysis was able to show the presence of a low percentage of CuII oxides (CuO or Cu(OH)2) with predominantly CuI oxide (Cu2O) which is not evident in Cu 2p XPS spectra.

Fish Food in the Deep Sea: Revisiting the Role of Large Food-Falls

PubMed Central

Higgs, Nicholas D.; Gates, Andrew R.; Jones, Daniel O. B.

2014-01-01

The carcasses of large pelagic vertebrates that sink to the seafloor represent a bounty of food to the deep-sea benthos, but natural food-falls have been rarely observed. Here were report on the first observations of three large ‘fish-falls’ on the deep-sea floor: a whale shark (Rhincodon typus) and three mobulid rays (genus Mobula). These observations come from industrial remotely operated vehicle video surveys of the seafloor on the Angola continental margin. The carcasses supported moderate communities of scavenging fish (up to 50 individuals per carcass), mostly from the family Zoarcidae, which appeared to be resident on or around the remains. Based on a global dataset of scavenging rates, we estimate that the elasmobranch carcasses provided food for mobile scavengers over extended time periods from weeks to months. No evidence of whale-fall type communities was observed on or around the carcasses, with the exception of putative sulphide-oxidising bacterial mats that outlined one of the mobulid carcasses. Using best estimates of carcass mass, we calculate that the carcasses reported here represent an average supply of carbon to the local seafloor of 0.4 mg m−2d−1, equivalent to ∼4% of the normal particulate organic carbon flux. Rapid flux of high-quality labile organic carbon in fish carcasses increases the transfer efficiency of the biological pump of carbon from the surface oceans to the deep sea. We postulate that these food-falls are the result of a local concentration of large marine vertebrates, linked to the high surface primary productivity in the study area. PMID:24804731

Diamond ages from Victor (Superior Craton): Intra-mantle cycling of volatiles (C, N, S) during supercontinent reorganisation

NASA Astrophysics Data System (ADS)

Aulbach, S.; Creaser, Robert A.; Stachel, Thomas; Heaman, Larry M.; Chinn, Ingrid L.; Kong, Julie

2018-05-01

The central Superior Craton hosts both the diamondiferous 1.1 Ga Kyle Lake and Jurassic Attawapiskat kimberlites. A major thermal event related to the Midcontinent Rift at ca. 1.1 Ga induced an elevated geothermal gradient that largely destroyed an older generation of diamonds, raising the question of when, and how, the diamond inventory beneath Attawapiskat was formed. We determined Re-Os isotope systematics of sulphides included in diamonds from Victor by isotope dilution negative thermal ionisation mass spectrometry in order to obtain insights into the age and nature of the diamond source in the context of regional tectonothermal evolution. Regression of the peridotitic inclusion data (n = 14 of 16) yields a 718 ± 49 Ma age, with an initial 187Os/188Os ratio of 0.1177 ± 0.0016, i.e. depleted at the time of formation (γOs -3.7 ± 1.3). Consequently, Re depletion model ages calculated for these samples are systematically overestimated. Given that reported 187Os/188Os in olivine from Attawapiskat xenoliths varies strongly (0.1012-0.1821), the low and nearly identical initial Os of sulphide inclusions combined with their high 187Re/188Os (median 0.34) suggest metasomatic formation from a mixed source. This was likely facilitated by percolation of amounts of melt sufficient to homogenise Os, (re)crystallise sulphide and (co)precipitate diamond; that is, the sulphide inclusions and their diamond host are synchronous if not syngenetic. The ∼720 Ma age corresponds to rifting beyond the northern craton margin during Rodinia break-up. This suggests mobilisation of volatiles (C, N, S) and Os due to attendant mantle stretching and metasomatism by initially oxidising and S-undersaturated melts, which ultimately produced lherzolitic diamonds with high N contents compared to older Kyle Lake diamonds. Thus, some rift-influenced settings are prospective with respect to diamond formation. They are also important sites of hidden, intra-lithospheric volatile redistribution that can be revealed by diamond studies. Later emplacement of the Attawapiskat kimberlites, linking the carbon cycle to the surface, was associated with renewed disturbance during passage of the Great Meteor Hotspot. Lherzolitic diamond formation from oxidising small-volume melts may be the expression of an early and deep stage of the lithospheric conditioning required for the successful eruption of kimberlites, which complements the late and shallow emplacement of volatile-rich metasomes after upward displacement of a redox freezing front.

Composition of the humin fraction of Terra Preta de Índios soils by NMR and multivariate curve resolution

NASA Astrophysics Data System (ADS)

Novotny, E. H.; Hayes, M. H. B.; Song, G.; Deazevedo, E. R.; Bonagamba, T. J.

2009-04-01

Most of the soils in the Amazon Region are acid, with low cation-exchange capacity (CEC) values, low fertility, and low production potential. There exists a class soils in this environment that have an archeo-anthropedogenic horizon of pre-Columbian origin, called "Terra Preta de Índios" (TPI), also known as Amazonian Dark Earths. These soils are characterized by higher fertility and more stable organic matter (OM) than the surrounding soils. The high fertility of TPI, and especially their sustainability, is attributed to the high levels of OM and to their physical-chemical properties. Up to 35-45% of the organic C in TPI is in the form of pyrogenic carbon (black carbon), compared to 14% in surrounding soils lacking an archeo-anthropedogenic horizon. Pyrogenic carbon derived from the partial carbonization of ligno-cellulosic materials, is composed of hydrogen-deficient condensed aromatic structures and, as the result of chemical and biochemical transformations, has a high charge density from carboxylic groups linked mainly to the aromatic core. Humin is the most recalcitrant and least understood fraction of soil OM. By definition, humin is the fraction that is not soluble in traditional aqueous alkaline soil extractants. It represents more than 50% of the soil organic carbon (OC) in mineral soils and more than 70% of the OC of lithified sediments, and is therefore the most important pool of the soil OM. However, for a study of humin by NMR it is necessary to isolate it and to achieve a degree of fractionation/purification. In this regard, an appropriate procedure1 has been applied to two soil samples from TPI and the material obtained was studied by solid state 13C NMR. The data analyses were carried out by Multivariate Curve Resolution (MCR). Results and Discussion MCR resolved the spectral matrix into three components, and these can be attributed to wood, humin, and oxidised charcoal materials The spectrum for the wood component agrees very well with that of eucalyptus wood. On the other hand, the humin spectrum shows an intense signal in the alkyl region (0-40 ppm) with a prominent signal for crystalline polymethylene at 33 ppm. These signals, in association with the carboxyl signal (173 ppm), indicate fatty acid origins for these components. Additionally, some altered aromatic structures (a broad and featureless signal centred at 130 ppm) and cellulosic material (110 and 70 ppm) were also evident. The broad signal at 54 ppm was probably from N-alkyl compounds from proteinaceous material since the corresponding O-aryl signal from the alternative methoxyl contribution was lacking. Finally, the oxidised char component was characterised by the broad and featureless signal at 128 ppm and the carboxyl at 172 ppm. The shoulder at 167 ppm gave evidence for carboxyl directly attached to the aromatic backbone. This char component also had minor contributions from aliphatic compounds, such as alkyl, N-alkyl, methoxyl, and carbohydrates. With regard to the estimated concentrations of each of these components, the coarse char samples and the residual humin (before and after DMSO/H2SO4 extraction) presented a higher content of unaltered wood (cellulose and lignin) material. The humin extracted by DMSO/H2SO4 was very rich in long chain aliphatic compounds (alkyl groups: 0-40 ppm). This lipidic fraction was also extracted by the alkali urea treatment and by soil dispersion using ultrasounic vibration. Greater amounts of oxidised char were also isolated following the ultrasonic treatment. This component remained in the residual humin, and it was also abundant in the coarse char fraction, indicating that the solvent systems adopted were unable to solubilise these materials. The extractable humin probably corresponds to fatty acids associated with the clay fraction and the un-extractable fraction was probably composed of particulate char (partially, and oxidised) and vegetable tissues. In conclusion, the extractable humin in these soils is mainly composed of hydrophobic compounds strongly associated with the mineral fraction. The DMSO/H2SO4 solvent is very efficient for solubilising these lipidic compounds. On the other hand, the disruption of the clay aggregates, by ultrasonication, allows additional oxidised char to be released and solubilised by the DMSO/acid and by the alkaline urea systems. Acknowledgements. The authors are grateful for support from Science Foundation Ireland, from Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro - Brazil, and from Fundação de Amparo à Pesquisa do Estado de São Paulo - Brazil.

Problems Caused by Microbes and Treatment Strategies Monitoring and Preventing Reservoir Souring Using Molecular Microbiological Methods (MMM)

NASA Astrophysics Data System (ADS)

Gittel, Antje

The injection of seawater during the process of secondary oil recovery in offshore oilfields supplies huge amounts of sulphate to the prokaryotic reservoir communities. Together with the presence of oil organics and their degradation products as electron donors, this facilitates the enrichment and growth of sulphate-reducing prokaryotes (SRP) in the reservoir, as well as in pipings and top-side installations (Sunde and Torsvik, 2005; Vance and Thrasher, 2005). The activity of SRP causes severe economic problems due to the reactivity and toxicity of the produced hydrogen sulphide (H2S), one of the major problems being reservoir souring. Besides the use of broad-spectrum biocides or inhibitors for sulphate reduction, the addition of nitrate effectively decreased the net production of H2S in model column studies (Myhr et al., 2002; Hubert et al., 2005; Dunsmore et al., 2006) and field trials (Telang et al., 1997; Bødtker et al., 2008). The mechanisms by which nitrate addition might affect souring control are (i) the stimulation of heterotrophic nitrate-reducing bacteria (hNRB) that outcompete SRP for electron donors, (ii) the activity of nitrate-reducing, sulphide-oxidising bacteria (NR-SOB), and (iii) the inhibition of SRP by the production of nitrite and nitrous oxides (Sunde and Torsvik, 2005; Hubert and Voordouw, 2007).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Platero-Prats, Ana E.; Li, Zhanyong; Gallington, Leighanne C.

Here, we explore the dynamic structure and reactivity of Cu species supported on NU-1000. By combining pair distribution function (PDF) analysis and difference envelope density (DED) analysis ofin situsynchrotron-based X-ray scattering data, we simultaneously probe the local structure of supported Cu-species, their distribution within NU-1000 and distortions of the NU-1000 lattice under conditions relevant to catalysis and catalyst activation. Our analyses show that atomic layer deposition (ALD) of Cu in NU-1000 (Cu-AIM) leads to the formation of Cu-oxo clusters within the small pores that connect the triangular and hexagonal channels. Exposure of Cu-AIM to a reducing atmosphere at 200 °Cmore » produces metallic Cu 0of two distinct particle sizes: ~4 nm nanoparticles and small sub-nanometer clusters. The size of these nanoparticles appears to be constrained by NU-1000 pore dimensions, with evidence of the sub-nanometer clusters being bound within the triangular channels flanked by pyrene rings. This supported Cu 0–NU-1000 system is catalytically active for gas-phase ethylene hydrogenation. Exposure of the catalyst to oxidative atmosphere re-oxidises the Cu species to a Cu 2O cuprite phase. The dynamic restructuring of the system in different chemical environments underscores the importance of probing these systemsin situ.« less

Evaluation of different nitrous oxide production models with four continuous long-term wastewater treatment process data series.

PubMed

Spérandio, Mathieu; Pocquet, Mathieu; Guo, Lisha; Ni, Bing-Jie; Vanrolleghem, Peter A; Yuan, Zhiguo

2016-03-01

Five activated sludge models describing N2O production by ammonium oxidising bacteria (AOB) were compared to four different long-term process data sets. Each model considers one of the two known N2O production pathways by AOB, namely the AOB denitrification pathway and the hydroxylamine oxidation pathway, with specific kinetic expressions. Satisfactory calibration could be obtained in most cases, but none of the models was able to describe all the N2O data obtained in the different systems with a similar parameter set. Variability of the parameters can be related to difficulties related to undescribed local concentration heterogeneities, physiological adaptation of micro-organisms, a microbial population switch, or regulation between multiple AOB pathways. This variability could be due to a dependence of the N2O production pathways on the nitrite (or free nitrous acid-FNA) concentrations and other operational conditions in different systems. This work gives an overview of the potentialities and limits of single AOB pathway models. Indicating in which condition each single pathway model is likely to explain the experimental observations, this work will also facilitate future work on models in which the two main N2O pathways active in AOB are represented together.

Acetic acid bacteria in traditional balsamic vinegar: phenotypic traits relevant for starter cultures selection.

PubMed

Gullo, Maria; Giudici, Paolo

2008-06-30

This review focuses on acetic acid bacteria in traditional balsamic vinegar process. Although several studies are available on acetic acid bacteria ecology, metabolism and nutritional requirements, their activity as well as their technological traits in homemade vinegars as traditional balsamic vinegar is not well known. The basic technology to oxidise cooked grape must to produce traditional balsamic vinegar is performed by the so called "seed-vinegar" that is a microbiologically undefined starter culture obtained from spontaneous acetification of previous raw material. Selected starter cultures are the main technological improvement in order to innovate traditional balsamic vinegar production but until now they are rarely applied. To develop acetic acid bacteria starter cultures, selection criteria have to take in account composition of raw material, acetic acid bacteria metabolic activities, applied technology and desired characteristics of the final product. For traditional balsamic vinegar, significative phenotypical traits of acetic acid bacteria have been highlighted. Basic traits are: ethanol preferred and efficient oxidation, fast rate of acetic acid production, tolerance to high concentration of acetic acid, no overoxidation and low pH resistance. Specific traits are tolerance to high sugar concentration and to a wide temperature range. Gluconacetobacter europaeus and Acetobacter malorum strains can be evaluated to develop selected starter cultures since they show one or more suitable characters.

Dietary glutamine supplementation effects on amino acid metabolism, intestinal nutrient absorption capacity and antioxidant response of gilthead sea bream (Sparus aurata) juveniles.

PubMed

Coutinho, F; Castro, C; Rufino-Palomares, E; Ordóñez-Grande, B; Gallardo, M A; Oliva-Teles, A; Peres, H

2016-01-01

A study was undertaken to evaluate dietary glutamine supplementation effects on gilthead sea bream performance, intestinal nutrient absorption capacity, hepatic and intestinal glutamine metabolism and oxidative status. For that purpose gilthead sea bream juveniles (mean weight 13.0g) were fed four isolipidic (18% lipid) and isonitrogenous (43% protein) diets supplemented with 0, 0.5, 1 and 2% glutamine for 6weeks. Fish performance, body composition and intestinal nutrient absorption capacity were not affected by dietary glutamine levels. Hepatic and intestinal glutaminase (GlNase), glutamine synthetase (GSase), alanine aminotransferase, aspartate aminotransferase and glutamate dehydrogenase activities were also unaffected by dietary glutamine supplementation. In the intestine GlNase activity was higher and GSase/GlNase ratio was two-fold lower than in the liver, suggesting a higher use of glutamine for energy production by the intestine than by the liver. The liver showed higher catalase and glucose-6-phosphate dehydrogenase activities, while the intestine presented higher glutathione peroxidase and glutathione reductase activities and oxidised glutathione content, which seems to reveal a higher glutathione dependency of the intestinal antioxidant response. Total and reduced glutathione contents in liver and intestine and superoxide dismutase activity in the intestine were enhanced by dietary glutamine, though lipid peroxidation values were not affected. Overall, differences between liver and intestine glutamine metabolism and antioxidant response were identified and the potential of dietary glutamine supplementation to gilthead sea bream's antioxidant response was elucidated. Copyright © 2015 Elsevier Inc. All rights reserved.

Calcium and Superoxide-Mediated Pathways Converge to Induce Nitric Oxide-Dependent Apoptosis in Mycobacterium fortuitum-Infected Fish Macrophages.

PubMed

Datta, Debika; Khatri, Preeti; Banerjee, Chaitali; Singh, Ambika; Meena, Ramavatar; Saha, Dhira Rani; Raman, Rajagopal; Rajamani, Paulraj; Mitra, Abhijit; Mazumder, Shibnath

2016-01-01

Mycobacterium fortuitum causes 'mycobacteriosis' in wide range of hosts although the mechanisms remain largely unknown. Here we demonstrate the role of calcium (Ca+2)-signalling cascade on M. fortuitum-induced apoptosis in headkidney macrophages (HKM) of Clarias sp. M. fortuitum could trigger intracellular-Ca+2 influx leading to the activation of calmodulin (CaM), protein kinase C alpha (PKCα) and Calmodulin kinase II gamma (CaMKIIg). Gene silencing and inhibitor studies established the role of CaM in M. fortuitum pathogenesis. We noted that CaMKIIg activation is regulated by CaM as well as PKCα-dependent superoxide anions. This is altogether first report of oxidised CaMKIIg in mycobacterial infections. Our studies with targeted-siRNA and pharmacological inhibitors implicate CaMKIIg to be pro-apoptotic and critical for the activation of extra-cellular signal regulated kinase 1/2 (ERK1/2). Inhibiting the ERK1/2 pathway attenuated nitric oxide synthase 2 (NOS2)-induced nitric oxide (NO) production. Conversely, inhibiting the NOS2-NO axis by specific-siRNA and inhibitors down-regulated ERK1/2 activation suggesting the crosstalk between ERK1/2 and NO is essential for pathogenesis induced by the bacterium. Silencing the NOS2-NO axis enhanced intracellular bacterial survival and attenuated caspase-8 mediated activation of caspase-3 in the infected HKM. Our findings unveil hitherto unknown mechanism of M. fortuitum pathogenesis. We propose that M. fortuitum triggers intracellular Ca+2 elevations resulting in CaM activation and PKCα-mediated superoxide generation. The cascade converges in common pathway mediated by CaMKIIg resulting in the activation of ERK1/2-NOS2 axis. The crosstalk between ERK1/2 and NO shifts the balance in favour of caspase dependent apoptosis of M. fortuitum-infected HKM.

Detonation models of fast combustion waves in nanoscale Al-MoO3 bulk powder media

NASA Astrophysics Data System (ADS)

Shaw, Benjamin D.; Pantoya, Michelle L.; Dikici, Birce

2013-02-01

The combustion of nanometric aluminum (Al) powder with an oxidiser such as molybdenum trioxide (MoO3) is studied analytically. This study focuses on detonation wave models and a Chapman-Jouget detonation model provides reasonable agreement with experimentally-observed wave speeds provided that multiphase equilibrium sound speeds are applied at the downstream edge of the detonation wave. The results indicate that equilibrium sound speeds of multiphase mixtures can play a critical role in determining speeds of fast combustion waves in nanoscale Al-MoO3 powder mixtures.

Uses of Laccases in the Food Industry

PubMed Central

Osma, Johann F.; Toca-Herrera, José L.; Rodríguez-Couto, Susana

2010-01-01

Laccases are an interesting group of multi copper enzymes, which have received much attention of researchers in the last decades due to their ability to oxidise both phenolic and nonphenolic lignin-related compounds as well as highly recalcitrant environmental pollutants. This makes these biocatalysts very useful for their application in several biotechnological processes, including the food industry. Thus, laccases hold great potential as food additives in food and beverage processing. Being energy-saving and biodegradable, laccase-based biocatalysts fit well with the development of highly efficient, sustainable, and eco-friendly industries. PMID:21048873

Transmission electron microscope analyses of alteration phases in martian meteorite MIL 090032

NASA Astrophysics Data System (ADS)

Hallis, L. J.; Ishii, H. A.; Bradley, J. P.; Taylor, G. J.

2014-06-01

The nakhlite group of martian meteorites found in the Antarctic contain varying abundances of both martian and terrestrial secondary alteration phases. The aim of this study was to use transmission electron microscopy (TEM) to compare martian and terrestrial alteration embodied within a single nakhlite martian meteorite find - MIL 090032. Martian alteration veins in MIL 090032 are composed of poorly ordered Fe-smectite phyllosilicate. This poorly-ordered smectite appears to be equivalent to the nanocrystalline phyllosilicate/hydrated amorphous gel phase previously described in the martian alteration veins of other nakhlites. Chemical differences in this nanocrystalline phyllosilicate between different nakhlites imply localised alteration, which occurred close to the martian surface in MIL 090032. Both structurally and compositionally the nakhlite nanocrystalline phyllosilicate shows similarities to the amorphous/poorly ordered phase recently discovered in martian soil by the Mars Curiosity Rover at Rocknest, Gale Crater. Terrestrially derived alteration phases in MIL 090032 include jarosite and gypsum, amorphous silicates, and Fe-oxides and hydroxides. Similarities between the mineralogy and chemistry of the MIL 090032 terrestrial and martian alteration phases suggest the alteration conditions on Mars were similar to those in the Antarctic. At both sites a small amount of fluid at low temperatures infiltrated the rock and became acidic as a result of the conversion of Fe2+ to Fe3+ under oxidising conditions.

Use of biogenic and abiotic elemental selenium nanospheres to sequester elemental mercury released from mercury contaminated museum specimens.

PubMed

Fellowes, J W; Pattrick, R A D; Green, D I; Dent, A; Lloyd, J R; Pearce, C I

2011-05-30

Mercuric chloride solutions have historically been used as pesticides to prevent bacterial, fungal and insect degradation of herbarium specimens. The University of Manchester museum herbarium contains over a million specimens from numerous collections, many preserved using HgCl(2) and its transformation to Hg(v)(0) represents a health risk to herbarium staff. Elevated mercury concentrations in work areas (∼ 1.7 μg m(-3)) are below advised safe levels (<25 μg m(-3)) but up to 90 μg m(-3) mercury vapour was measured in specimen boxes, representing a risk when accessing the samples. Mercury vapour release correlated strongly with temperature. Mercury salts were observed on botanical specimens at concentrations up to 2.85 wt% (bulk); XPS, SEM-EDS and XANES suggest the presence of residual HgCl(2) as well as cubic HgS and HgO. Bacterially derived, amorphous nanospheres of elemental selenium effectively sequestered the mercury vapour in the specimen boxes (up to 19 wt%), and analysis demonstrated that the Hg(v)(0) was oxidised by the selenium to form stable HgSe on the surface of the nanospheres. Biogenic Se(0) can be used to reduce Hg(v)(0) in long term, slow release environments. Copyright © 2011 Elsevier B.V. All rights reserved.

The impact of gender and age on the nutritional parameters of alpaca (Vicugna pacos) meat, colour stability and fat traits.

PubMed

Smith, M A; Bush, R D; van de Ven, R J; Hall, E J S; Greenwood, P L; Hopkins, D L

2017-01-01

Meat quality parameters for 50 huacaya alpacas, representing three age groups (18, 24 and 36months) and two genders (females and castrated males) were studied. Prior to chilling, samples of m. longissimus thoracis et lumborum (LL) were taken to determine isocitrate dehydrogenase activity and glycogen concentration, and further meat quality samples were taken after 24h. Alpaca meat has low levels (<1%) of intramuscular fat in the LL, m. semimembranosus and m. biceps femoris, but the level in the LL increases with animal age, with levels of desirable polyunsaturated fatty acids (PUFA) ranging from 96.3 to 136.4mg/100g. Lipid oxidisation post retail display ranged from 1.27 to 1.96MDA/kg meat. Colour stability testing indicated alpaca meat was relatively stable during retail display with day of display having no significant effect on lightness (L*), or the 630nm/580nm ratio. These results may relate to the high proportion (76%) of glycolytic and type IIX muscle fibres in LL. Copyright © 2016 Elsevier Ltd. All rights reserved.

From urban municipalities to polar bioremediation: the characterisation and contribution of biogenic minerals for water treatment.

PubMed

Freidman, Benjamin L; Northcott, Kathy A; Thiel, Peta; Gras, Sally L; Snape, Ian; Stevens, Geoff W; Mumford, Kathryn A

2017-06-01

Minerals of biological origin have shown significant potential for the separation of contaminants from water worldwide. This study details the contribution of biologically derived minerals to water treatment operations, with a focus on filtration media from urban municipalities and remote cold regions. The results support biofilm-embedded iron and manganese to be the building blocks of biogenic mineral development on activated carbon and nutrient-amended zeolites. The presence of similar iron and manganese oxidising bacterial species across all filter media supports the analogous morphologies of biogenic minerals between sites and suggests that biological water treatment processes may be feasible across a range of climates. This is the first time the stages of biogenic mineral formation have been aligned with comprehensive imaging of the biofilm community and bacterial identification; especially with respect to cold regions. Where biogenic mineral formation occurs on filter media, the potential exists for enhanced adsorption for a range of organic and inorganic contaminants and improved longevity of filter media beyond the adsorption or exchange capacities of the raw material.

Mitochondria from the left heart ventricles of both normotensive and spontaneously hypertensive rats oxidize externally added NADH mostly via a novel malate/oxaloacetate shuttle as reconstructed in vitro.

PubMed

Atlante, Anna; Seccia, Teresa M; De Bari, Lidia; Marra, Ersilia; Passarella, Salvatore

2006-07-01

A substantial increase in NADH production, arising from accelerated glycolysis, occurs in cardiac hypertrophy and this raises the question of how the NADH is oxidised. We have addressed this problem by reconstructing appropriate mitochondrial shuttles in vitro, using mitochondria from the left ventricles of both normotensive and spontaneously hypertensive rats at 5 and 24 weeks of age as model systems for left ventricle hypertrophy and hypertrophy/hypertension respectively. We found that most NADH oxidation occurs via a novel malate/oxaloacetate shuttle, the activity of which increases with time and with the progression of hypertrophy and development of hypertension as judged by statistical ANOVA analysis. In contrast, alpha-glycerol-phosphate and the malate/aspartate shuttles were shown to make only a minor contribution to NADH oxidation in a manner essentially independent of age and progression of hypertrophy/hypertension. The rate of malate transport in exchange with oxaloacetate proved to limit the rate of NADH oxidation via this malate/oxaloacetate shuttle.

Chromite oxidation by manganese oxides in subseafloor basalts and the presence of putative fossilized microorganisms.

PubMed

Ivarsson, Magnus; Broman, Curt; Holm, Nils G

2011-06-03

Chromite is a mineral with low solubility and is thus resistant to dissolution. The exception is when manganese oxides are available, since they are the only known naturally occurring oxidants for chromite. In the presence of Mn(IV) oxides, Cr(III) will oxidise to Cr(VI), which is more soluble than Cr(III), and thus easier to be removed. Here we report of chromite phenocrysts that are replaced by rhodochrosite (Mn(II) carbonate) in subseafloor basalts from the Koko Seamount, Pacific Ocean, that were drilled and collected during the Ocean Drilling Program (ODP) Leg 197. The mineral succession chromite-rhodochrosite-saponite in the phenocrysts is interpreted as the result of chromite oxidation by manganese oxides. Putative fossilized microorganisms are abundant in the rhodochrosite and we suggest that the oxidation of chromite has been mediated by microbial activity. It has previously been shown in soils and in laboratory experiments that chromium oxidation is indirectly mediated by microbial formation of manganese oxides. Here we suggest a similar process in subseafloor basalts.

Chromite oxidation by manganese oxides in subseafloor basalts and the presence of putative fossilized microorganisms

PubMed Central

2011-01-01

Chromite is a mineral with low solubility and is thus resistant to dissolution. The exception is when manganese oxides are available, since they are the only known naturally occurring oxidants for chromite. In the presence of Mn(IV) oxides, Cr(III) will oxidise to Cr(VI), which is more soluble than Cr(III), and thus easier to be removed. Here we report of chromite phenocrysts that are replaced by rhodochrosite (Mn(II) carbonate) in subseafloor basalts from the Koko Seamount, Pacific Ocean, that were drilled and collected during the Ocean Drilling Program (ODP) Leg 197. The mineral succession chromite-rhodochrosite-saponite in the phenocrysts is interpreted as the result of chromite oxidation by manganese oxides. Putative fossilized microorganisms are abundant in the rhodochrosite and we suggest that the oxidation of chromite has been mediated by microbial activity. It has previously been shown in soils and in laboratory experiments that chromium oxidation is indirectly mediated by microbial formation of manganese oxides. Here we suggest a similar process in subseafloor basalts. PMID:21639896

Characterization of the deep microbial life in the Altmark natural gas reservoir

NASA Astrophysics Data System (ADS)

Morozova, D.; Alawi, M.; Vieth-Hillebrand, A.; Kock, D.; Krüger, M.; Wuerdemann, H.; Shaheed, M.

2010-12-01

Within the framework of the CLEAN project (CO2 Largescale Enhanced gas recovery in the Altmark Natural gas field) technical basics with special emphasis on process monitoring are explored by injecting CO2 into a gas reservoir. Our study focuses on the investigation of the in-situ microbial community of the Rotliegend natural gas reservoir in the Altmark, located south of the city Salzwedel, Germany. In order to characterize the microbial life in the extreme habitat we aim to localize and identify microbes including their metabolism influencing the creation and dissolution of minerals. The ability of microorganisms to speed up dissolution and formation of minerals might result in changes of the local permeability and the long-term safety of CO2 storage. However, geology, structure and chemistry of the reservoir rock and the cap rock as well as interaction with saline formation water and natural gases and the injected CO2 affect the microbial community composition and activity. The reservoir located at the depth of approximately 3500 m, is characterised by high salinity (420 g/l) and temperatures up to 127°C. It represents an extreme environment for microbial life and therefore the main focus is on hyperthermophilic, halophilic anaerobic microorganisms. In consequence of the injection of large amounts of CO2 in the course of a commercial EGR (Enhanced Gas Recovery), the environmental conditions (e.g. pH, temperature, pressure and solubility of minerals) for the autochthonous microorganisms will change. Genetic profiling of amplified 16S rRNA genes are applied for detecting structural changes in the community by using PCR- SSCP (PCR-Single-Strand-Conformation Polymorphism), DGGE (Denaturing Gradient Gel Electrophoresis) and 16S rRNA cloning. First results of the baseline survey indicate the presence of microorganisms similar to representatives from other deep environments. The sequence analyses revealed the presence of several H2-oxidising bacteria (Hydrogenophaga sp., Adicdovorax sp., Ralstonia sp., Pseudomonas sp.), thiosulfate-oxidising bacteria (Diaphorobacter sp.) and biocorrosive thermophilic microorganisms, which have not previously been cultivated. Furthermore, several uncultivated microorganisms were found, that were similar to representatives from other saline, hot, anoxic, deep environments. However, due to the hypersaline and hyperthermophilic reservoir conditions, cell numbers are low, so that the quantification of those microorganisms as well as the determination of microbial activity was not yet possible. Microbial monitoring methods have to be further developed to study microbial activities under these extreme conditions to access their influence on the EGR technique and on enhancing the long term safety of the process by fixation of carbon dioxide by precipitation of carbonates. We thank GDF SUEZ for providing the data for the Rotliegend reservoir, sample material and supporting sampling campaigns. The CLEAN project is funded by the German Federal Ministry of Education and Research (BMBF) in the framework of the GEOTECHNOLOGIEN Program.

Monte Carlo Simulation of Callisto's Exosphere

NASA Astrophysics Data System (ADS)

Vorburger, Audrey; Wurz, Peter; Galli, André; Mousis, Olivier; Barabash, Stas; Lammer, Helmut

2014-05-01

Whereas Callisto's surface has been mapped as early as in 1980 by the two Voyager missions, Callisto's tenuous atmosphere, also called an exosphere, was not directly observed until the Galileo mission in 1999. The Galileo Near-Infrared Mapping Spectrometer detected a CO2 signal up to 100 km above the surface [Carlson, Science, 1999]. Radio occultation measurements, also conducted by Galileo, led to the detection of an ionosphere with inferred densities much higher than can be explained by the measured CO2 exosphere, though [Kliore et al., J. Geophys. Res, 2002]. Insight about Callisto's exosphere is expected to be boosted by the Neutral Ion Mass Spectrometer (NIM) of the Particle Environment Package (PEP) on board the planned JUpiter ICy moons Explorer (JUICE) mission, which will conduct the first-ever direct sampling of the exospheres of Europa, Ganymede, and Callisto. To ensure that NIM's mass resolution and mass range will be sufficient for NIM to detect most expected species in Callisto's exosphere, we model said exosphere ab initio. Since Callisto is thought to consist to about equal parts of both icy and rocky components [Showman and Malhotra, Science, 1999], we model particle release from an icy as well as from a mineral surface separately. For the ice component, we investigate two different compositions, for reducing and oxidising conditions, which find analogy in the initial gas phase conditions in the solar nebula [Mousis et al., Planet. Space Sci., submitted]. For the non-ice material, the mineral surface, we investigate surfaces with compositions similar to CI chondrites and L/LL type chondrites, both of which have been suggested to represent Callisto's non-ice material best [Kuskov and Kronrod, Icarus, 2005 and Moore et al., Cambridge University Press, 2004]. For all mentioned materials, we compute density profiles for particles released by either surface sublimation or ion induced sputtering up to an altitude of 100'000 km. Our results show that close to the surface the sublimated particles dominate the day-side exosphere, however, their density profiles (with the exception of H and H2) decrease much more rapidly with altitude than those of the sputtered particles, thus, the latter particles start to dominate at altitudes above ~1000 km. Since the JUICE flybys are as low as 200 km above Callisto's surface, NIM is expected to register both the sublimated as well as sputtered particle populations. Our simulations show that NIM's sensitivity is high enough to allow the detection of particles sputtered from the icy as well as the mineral surfaces, and to distinguish between the different composition models.

Use of transcriptomic data for extending a model of the AppA/PpsR system in Rhodobacter sphaeroides.

PubMed

Pandey, Rakesh; Armitage, Judith P; Wadhams, George H

2017-12-28

Photosynthetic (PS) gene expression in Rhodobacter sphaeroides is regulated in response to changes in light and redox conditions mainly by PrrB/A, FnrL and AppA/PpsR systems. The PrrB/A and FnrL systems activate the expression of them under anaerobic conditions while the AppA/PpsR system represses them under aerobic conditions. Recently, two mathematical models have been developed for the AppA/PpsR system and demonstrated how the interaction between AppA and PpsR could lead to a phenotype in which PS genes are repressed under semi-aerobic conditions. These models have also predicted that the transition from aerobic to anaerobic growth mode could occur via a bistable regime. However, they lack experimentally quantifiable inputs and outputs. Here, we extend one of them to include such quantities and combine all relevant micro-array data publically available for a PS gene of this bacterium and use that to parameterise the model. In addition, we hypothesise that the AppA/PpsR system alone might account for the observed trend of PS gene expression under semi-aerobic conditions. Our extended model of the AppA/PpsR system includes the biological input of atmospheric oxygen concentration and an output of photosynthetic gene expression. Following our hypothesis that the AppA/PpsR system alone is sufficient to describe the overall trend of PS gene expression we parameterise the model and suggest that the rate of AppA reduction in vivo should be faster than its oxidation. Also, we show that despite both the reduced and oxidised forms of PpsR binding to the PS gene promoters in vitro, binding of the oxidised form as a repressor alone is sufficient to reproduce the observed PS gene expression pattern. Finally, the combination of model parameters which fit the biological data well are broadly consistent with those which were previously determined to be required for the system to show (i) the repression of PS genes under semi-aerobic conditions, and (ii) bistability. We found that despite at least three pathways being involved in the regulation of photosynthetic genes, the AppA/PpsR system alone is capable of accounting for the observed trends in photosynthetic gene expression seen at different oxygen levels.

Impact of prechlorination on organophosphorus pesticides during drinking water treatment: Removal and transformation to toxic oxon byproducts.

PubMed

Li, Wei; Wu, Ruiqing; Duan, Jinming; Saint, Christopher P; van Leeuwen, John

2016-11-15

Prechlorination is commonly used to minimize operational problems associated with biological growth as well as taste and odor control during drinking water treatment. However, prechlorination can also oxidise micropollutants into intermediate byproducts. This could impose profound effects on the safety of the finished water if the transformed byproducts are more toxic and less removable. This study investigated the effect of prechlorination on decomposition and subsequent removal of the four organophosphorus pesticides (OPPs): chlorpyrifos, diazinon, malathion and tolclofos-methyl using a simulated conventional water treatment process of powdered activated carbon assisted coagulation-sedimentation-filtration (PAC-CSF) and postchlorination. It was found that, following prechlorination, not only did the percentage of OPPs oxidation vary significantly, but also the concentration of transformed oxons, which are more toxic than their parent compounds, increased as the major identified oxidation byproducts in water. Removal of these oxons proved to be more difficult by the PAC-CSF than their parent OPPs, because they are more water soluble and more hydrophilic. Both the OPP oxidation and oxon formation increased with chlorine dose during prechlorination. Meanwhile, the continuing chlorination of OPPs by residual free chlorine during PAC-CSF further complicated the pesticide removal processes, generally resulting in a gradually increased formation of oxons. Moreover, in the final treatment stage of postchlorination, the more chlorine-reactive pesticides, malathion and diazinon, were completely oxidised and the formation of corresponding oxons was increased with the prechlorine dose. In contrast, a certain amount of the less chlorine-reactive pesticide tolclofos-methyl still remained in solution after postchlorination, accompanied by an increased formation of tolclofos-methyl oxon with prechlorine dose. Since the oxons are resistant to further oxidation and less adsorbable during the PAC-CSF process, the gross removal of these pesticides and their oxons decreased with increase of the prechlorine dose. This led to an accumulation of the more toxic oxons in the finished water, especially at higher chlorine doses during prechlorination. The significance of this work is the demonstration that, under circumstances where prechlorination is used and source water contains traces of OPPs, alternative practices should be prioritized to avoid the potential risks involved in consumption of the treated water. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effect of g.9476869G>A myeloperoxidase (MPO) gene polymorphism on the antioxidant activity of milk from Polish Holstein-Friesian cows of the Black-and-White variety (HO).

PubMed

Pokorska, Joanna; Poskart, Karolina; Kułaj, Dominika; Ochrem, Andrzej; Dusza, Magdalena; Gil, Zygmunt; Świętek, Ewa; Makulska, Joanna

2017-05-01

Myeloperoxidase (MPO) is an important enzyme, which is one of the components of the antibacterial system in neutrophils and monocytes. MPO participates in the inflammatory response in multiple locations in the body, including the mammary glands. As a result of the activity of MPO, many oxidising compounds as well as reactive oxygen species are generated. It seems that myeloperoxidase may be a marker linking inflammation processes and oxidative stress. So far, there are no literature data on the association between the MPO gene polymorphism and the antioxidant properties of milk. The aim of the study was to analyse the effect of g.9476869G > A polymorphism of myeloperoxidase (MPO) gene and age of cows on the antioxidant activity of milk and other milk traits in Polish Holstein-Friesian cows. Polymorphism of MPO gene was identified by the PCR-RFLP method using the HphI endonuclease. The total antioxidant capacity of milk samples was measured by the Trolox Equivalent Antioxidant Capacity (TEAC) method. It was found that the GG genotype was the most frequent (0·606). The genotype at the tested MPO locus and the age of the animals affected the antioxidant activity of milk. Milk from cows with the GA genotype was characterised by a significantly higher antioxidant activity than milk from cows with the GG genotype (P < 0·0001). The analysis of interaction showed that cows with the GA genotype and older than 6·5 years produced milk with a significantly higher antioxidant activity compared with younger cows with the same genotype (P < 0·0001), as well as cows with the GG genotype of all ages (P < 0·0001).

High temperature investigation of the solid/liquid transition in the PuO2-UO2-ZrO2 system

NASA Astrophysics Data System (ADS)

Quaini, A.; Guéneau, C.; Gossé, S.; Sundman, B.; Manara, D.; Smith, A. L.; Bottomley, D.; Lajarge, P.; Ernstberger, M.; Hodaj, F.

2015-12-01

The solid/liquid transitions in the quaternary U-Pu-Zr-O system are of great interest for the analysis of core meltdown accidents in Pressurised Water Reactors (PWR) fuelled with uranium-dioxide and MOX. During a severe accident the Zr-based cladding can become completely oxidised due to the interaction with the oxide fuel and the water coolant. In this framework, the present analysis is focused on the pseudo-ternary system UO2-PuO2-ZrO2. The melting/solidification behaviour of five pseudo-ternary and one pseudo-binary ((PuO2)0.50(ZrO2)0.50) compositions have been investigated experimentally by a laser heating method under pre-set atmospheres. The effects of an oxidising or reducing atmosphere on the observed melting/freezing temperatures, as well as the amount of UO2 in the sample, have been clearly identified for the different compositions. The oxygen-to-metal ratio is a key parameter affecting the melting/freezing temperature because of incongruent vaporisation effects. In parallel, a detailed thermodynamic model for the UO2-PuO2-ZrO2 system has been developed using the CALPHAD method, and thermodynamic calculations have been performed to interpret the present laser heating results, as well as the high temperature behaviour of the cubic (Pu,U,Zr)O2±x-c mixed oxide phase. A good agreement was obtained between the calculated and experimental data points. This work enables an improved understanding of the major factors relevant to severe accident in nuclear reactors.

Abyssal and hydrated mantle wedge serpentinised peridotites: a comparison of the 15°20'N fracture zone and New Caledonia serpentinites

NASA Astrophysics Data System (ADS)

Mothersole, Fiona Elizabeth; Evans, Katy; Frost, B. Ronald

2017-08-01

Subduction of serpentinised mantle transfers oxidised and hydrated mantle lithosphere into the Earth, with consequences for the oxidation state of sub-arc mantle and the genesis of arc-related ore deposits. The role of subducted serpentinised mantle lithosphere in earth system processes is uncertain because subduction fluxes are poorly constrained. Most subducted serpentinised mantle is serpentinised on the ocean floor settings. Yet this material is poorly represented in the literature because it is difficult to access. Large volumes of accessible serpentinite are available in ophiolite complexes, and most interpretations of subduction fluxes associated with ultramafic rocks are based on ophiolite studies. Seafloor and ophiolite serpentinisation can occur under different conditions, so it is necessary to assess if ophiolite serpentinites are a good proxy for seafloor serpentinites. Serpentinites sampled during ODP cruise 209 were compared with serpentinites from New Caledonia. The ODP209 serpentinites were serpentinised by modified seawater in a shallow hydrothermal seafloor setting. The New Caledonia serpentinites were serpentinised in a mantle wedge setting by slab-derived fluids, with possible contributions from oceanic serpentinisation and post-obduction serpentinisation. Petrological, whole rock and mineralogical analyses were combined to compare the two sample sets. Petrologically, the evolution of serpentinisation was close to identical in the two environments. However, more oxidised iron, Cl, S and C is present in serpentine from the ODP209 serpentinites relative to the New Caledonia serpentinites. Given these observations, the use of serpentinites from different geodynamic settings as a proxy for abyssal serpentinites from spreading settings must be undertaken with caution.

Comparative c-type cytochrome expression analysis in Shewanella oneidensis strain MR-1 and Anaeromyxobacter dehalogenans strain 2CP-C grown with soluble and insoluble oxidised metal electron acceptors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nissen, Silke; Liu, Xiaoxin; Chourey, Karuna

2012-01-01

The genomes of Shewanella oneidensis strain MR-1 and Anaeromyxobacter dehalogenans strain 2CP-C encode 40 and 69 putative c-type cytochrome genes, respectively. Deletion mutant and biochemical studies have assigned specific functions to a few c-type cytochromes involved in electron transfer to oxidised metals in Shewanella oneidensis strain MR-1. Although promising, the genetic approach is limited to gene deletions that produce a distinct phenotype, and organism for which a genetic system is available. To more comprehensively investigate and compare c-type cytochrome expression in Shewanella oneidensis strain MR-1 and Anaeromyxobacter dehalogenans strain 2CP-C, proteomic measurements were used to characterise lysates of cells grownmore » with soluble Fe(III) (as ferric citrate) and insoluble Mn(IV) (as MnO2) as electron acceptors. Strain MR-1 expressed 19 and 20, and strain 2CP-C expressed 27 and 25 c-type cytochromes when grown with Fe(III) and Mn(IV), respectively. The majority of c-type cytochromes (77% for strain MR-1 and 63% for strain 2CP-C) were expressed under both growth conditions; however, the analysis also revealed unique c-type cytochromes that were specifically expressed in cells grown with soluble Fe(III) or insoluble Mn(IV). Proteomic characterisation proved to be a promising approach for determining the c-type cytochrome complement expressed under different growth conditions, and will help elucidating the specific functions of more c-type cytochromes that are the basis for Shewanella and Anaeromyxobacter respiratory versatility.« less

ECHMERIT: A new on-line global mercury-chemistry model

NASA Astrophysics Data System (ADS)

Jung, G.; Hedgecock, I. M.; Pirrone, N.

2009-04-01

Mercury is a volatile metal, that is of concern because when deposited and transformed to methylmercury accumulates within the food-web. Due to the long lifetime of elemental mercury, which is the dominant fraction of mercury species in the atmosphere, mercury is prone to long-range transport and therefore distributed over the globe, transported and hence deposited even in regions far from anthropogenic emission sources. Mercury is released to the atmosphere from a variety of natural and anthropogenic sources, in elementary and oxidised forms, and as particulate mercury. It is then transported, but also transformed chemically in the gaseous phase, as well as in aqueous phase within cloud and rain droplets. Mercury (particularly its oxidised forms) is removed from the atmosphere though wet and dry deposition processes, a large fraction of deposited mercury is, after chemical or biological reduction, re-emitted to the atmosphere as elementary mercury. To investigate mercury chemistry and transport processes on the global scale, the new, global model ECHMERIT has been developed. ECHMERIT simulates meteorology, transport, deposition, photolysis and chemistry on-line. The general circulation model on which ECHMERIT is based is ECHAM5. Sophisticated chemical modules have been implemented, including gas phase chemistry based on the CBM-Z chemistry mechanism, as well as aqueous phase chemistry, both of which have been adapted to include Hg chemistry and Hg species gas-droplet mass transfer. ECHMERIT uses the fast-J photolysis routine. State-of-the-art procedures simulating wet and dry deposition and emissions were adapted and included in the model as well. An overview of the model structure, development, validation and sensitivity studies is presented.

Human Cytomegalovirus-Encoded miR-US25-1 Aggravates the Oxidised Low Density Lipoprotein-Induced Apoptosis of Endothelial Cells

PubMed Central

Fan, Jianmin; Zhang, Wen; Liu, Qiming

2014-01-01

Human cytomegalovirus (HCMV) infection is linked to the development and severity of the cardiovascular disease atherosclerosis; however, there is little known about the promotion of atherosclerosis. miR-US25-1 is one of HCMV-encoded miRNAs and targets cellular genes that are essential for virus growth to control the life cycle of the virus and host cells. The prominent regulation on cell cycle genes of the miR-US25-1 attracts us to explore its role in the atherosclerosis promotion. It was indicated that miR-US25-1 level was upregulated in subjects or in endothelial cells with HCMV infection; and the miR-US25-1 downregulated the expression of BRCC 3 by targeting the 5′ UTR of BRCC 3. And a miR-US25-1 mimics transfection could reduce the EAhy926 cell viability but did not induce apoptosis in EAhy926 cells. And what is more, miR-US25-1 mimicis transfection deteriorated the ox-LDL-induced apoptosis and aggravated the upregulation of apoptosis-associated molecules by oxidised low density lipoprotein (ox-LDL) in EAhy926 cells. And we have also confirmed the deregulation of BRCC 3 expression by miR-US25-1 by targeting the 5′ UTR of it. Given the vital role of BRCC 3 in DNA damage repairing, we speculated that the targeting inhibition of BRCC 3 by miR-US25-1 may contribute to the aggravation of ox-LDL-promoted apoptosis of endothelial EAhy926 cells. PMID:24895586

Nitrogen fixation in the activated sludge treatment of thermomechanical pulping wastewater: effect of dissolved oxygen.

PubMed

Slade, A H; Anderson, S M; Evans, B G

2003-01-01

N-ViroTech, a novel technology which selects for nitrogen-fixing bacteria as the bacteria primarily responsible for carbon removal, has been developed to treat nutrient limited wastewaters to a high quality without the addition of nitrogen, and only minimal addition of phosphorus. Selection of the operating dissolved oxygen level to maximise nitrogen fixation forms a key component of the technology. Pilot scale activated sludge treatment of a thermomechanical pulping wastewater was carried out in nitrogen-fixing mode over a 15 month period. The effect of dissolved oxygen was studied at three levels: 14% (Phase 1), 5% (Phase 2) and 30% (Phase 3). The plant was operated at an organic loading of 0.7-1.1 kg BOD5/m3/d, a solids retention time of approximately 10 d, a hydraulic retention time of 1.4 d and a F:M ratio of 0.17-0.23 mg BOD5/mg VSS/d. Treatment performance was very stable over the three dissolved oxygen operating levels. The plant achieved 94-96% BOD removal, 82-87% total COD removal, 79-87% soluble COD removal, and >99% total extractives removal. The lowest organic carbon removals were observed during operation at 30% DO but were more likely to be due to phosphorus limitation than operation at high dissolved oxygen, as there was a significant decrease in phosphorus entering the plant during Phase 3. Discharge of dissolved nitrogen, ammonium and oxidised nitrogen were consistently low (1.1-1.6 mg/L DKN, 0.1-0.2 mg/L NH4+-N and 0.0 mg/L oxidised nitrogen). Discharge of dissolved phosphorus was 2.8 mg/L, 0.1 mg/L and 0.6 mg/L DRP in Phases 1, 2 and 3 respectively. It was postulated that a population of polyphosphate accumulating bacteria developed during Phase 1. Operation at low dissolved oxygen during Phase 2 appeared to promote biological phosphorus uptake which may have been affected by raising the dissolved oxygen to 30% in Phase 3. Total nitrogen and phosphorus discharge was dependent on efficient secondary clarification, and improved over the course of the study as suspended solids discharge improved. Nitrogen fixation was demonstrated throughout the study using an acetylene reduction assay. Based on nitrogen balances around the plant, there was a 55, 354 and 98% increase in nitrogen during Phases 1, 2 and 3 respectively. There was a significant decrease in phosphorus between Phases 1 and 2, and Phase 3 of the study, as well as a significant increase in nitrogen between Phases 2 and 3 which masked the effect of changing the dissolved oxygen. Operation at low dissolved oxygen appeared to confer a competitive advantage to the nitrogen-fixing bacteria.

Relating hygroscopicity and optical properties to chemical composition and structure of secondary organic aerosol particles generated from the ozonolysis of α-pinene

NASA Astrophysics Data System (ADS)

Denjean, C.; Formenti, P.; Picquet-Varrault, B.; Pangui, E.; Zapf, P.; Katrib, Y.; Giorio, C.; Tapparo, A.; Monod, A.; Temime-Roussel, B.; Decorse, P.; Mangeney, C.; Doussin, J. F.

2015-03-01

Secondary organic aerosol (SOA) were generated from the ozonolysis of α-pinene in the CESAM (French acronym for Experimental Multiphasic Atmospheric Simulation Chamber) simulation chamber. The SOA formation and aging were studied by following their optical, hygroscopic and chemical properties. The optical properties were investigated by determining the particle complex refractive index (CRI). The hygroscopicity was quantified by measuring the effect of relative humidity (RH) on the particle size (size growth factor, GF) and on the scattering coefficient (scattering growth factor, f(RH)). The oxygen to carbon atomic ratios (O : C) of the particle surface and bulk were used as a sensitive parameter to correlate the changes in hygroscopic and optical properties of the SOA composition during their formation and aging in CESAM. The real CRI at 525 nm wavelength decreased from 1.43-1.60 (±0.02) to 1.32-1.38 (±0.02) during the SOA formation. The decrease in the real CRI correlated to the O : C decrease from 0.68 (±0.20) to 0.55 (±0.16). In contrast, the GF remained roughly constant over the reaction time, with values of 1.02-1.07 (±0.02) at 90% (±4.2%) RH. Simultaneous measurements of O : C of the particle surface revealed that the SOA was not composed of a homogeneous mixture, but contained less oxidised species at the surface which may limit water absorption. In addition, an apparent change in both mobility diameter and scattering coefficient with increasing RH from 0 to 30% was observed for SOA after 14 h of reaction. We postulate that this change could be due to a change in the viscosity of the SOA from a predominantly glassy state to a predominantly liquid state.

Aqueous cationic, anionic and non-ionic multi-walled carbon nanotubes, functionalised with minimal framework damage, for biomedical application.

PubMed

Chen, Shu; Hu, Sheng; Smith, Elizabeth F; Ruenraroengsak, Pakatip; Thorley, Andrew J; Menzel, Robert; Goode, Angela E; Ryan, Mary P; Tetley, Teresa D; Porter, Alexandra E; Shaffer, Milo S P

2014-06-01

The use of a thermochemical grafting approach provides a versatile means to functionalise as-synthesised, bulk multi-walled carbon nanotubes (MWNTs) without altering their inherent structure. The associated retention of properties is desirable for a wide range of commercial applications, including for drug delivery and medical purposes; it is also pertinent to studies of intrinsic toxicology. A systematic series of water-compatible MWNTs, with diameter around 12 nm have been prepared, to provide structurally-equivalent samples predominantly stabilised by anionic, cationic, or non-ionic groups. The surface charge of MWNTs was controlled by varying the grafting reagents and subsequent post-functionalisation modifications. The degree of grafting was established by thermal analysis (TGA). High resolution transmission electron microscope (HRTEM) and Raman measurements confirmed that the structural framework of the MWNTs was unaffected by the thermochemical treatment, in contrast to a conventional acid-oxidised control which was severely damaged. The effectiveness of the surface modification was demonstrated by significantly improved solubility and stability in both water and cell culture medium, and further quantified by zeta-potential analysis. The grafted MWNTs exhibited relatively low bioreactivity on transformed human alveolar epithelial type 1-like cells (TT1) following 24 h exposure as demonstrated by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) and lactate dehydrogenase release (LDH) assays. The exposure of TT1 cells to MWNTs suppressed the release of the inflammatory mediators, interleukin 6 (IL-6) and interleukin 8 (IL-8). TEM cell uptake studies indicated efficient cellular entry of MWNTs into TT1 cells, via a range of mechanisms. Cationic MWNTs showed a more substantial interaction with TT1 cell membranes than anionic MWNTs, demonstrating a surface charge effect on cell uptake. Copyright © 2014 Elsevier Ltd. All rights reserved.

Distribution and activity of anaerobic ammonium-oxidising bacteria in natural freshwater wetland soils.

PubMed

Shen, Li-dong; Wu, Hong-sheng; Gao, Zhi-qiu; Cheng, Hai-xiang; Li, Ji; Liu, Xu; Ren, Qian-qi

2016-04-01

Anaerobic ammonium oxidation (anammox) process plays a significant role in the marine nitrogen cycle. However, the quantitative importance of this process in nitrogen removal in wetland systems, particularly in natural freshwater wetlands, is still not determined. In the present study, we provided the evidence of the distribution and activity of anammox bacteria in a natural freshwater wetland, located in southeastern China, by using (15)N stable isotope measurements, quantitative PCR assays and 16S rRNA gene clone library analysis. The potential anammox rates measured in this wetland system ranged between 2.5 and 25.5 nmol N2 g(-1) soil day(-1), and up to 20% soil dinitrogen gas production could be attributed to the anammox process. Phylogenetic analysis of 16S rRNA genes showed that anammox bacteria related to Candidatus Brocadia, Candidatus Kuenenia, Candidatus Anammoxoglobus and two novel anammox clusters coexisted in the collected soil cores, with Candidatus Brocadia and Candidatus Kuenenia being the dominant anammox genera. Quantitative PCR of hydrazine synthase genes showed that the abundance of anammox bacteria varied from 2.3 × 10(5) to 2.2 × 10(6) copies g(-1) soil in the examined soil cores. Correlation analyses suggested that the soil ammonium concentration had significant influence on the activity of anammox bacteria. On the basis of (15)N tracing technology, it is estimated that a total loss of 31.1 g N m(-2) per year could be linked the anammox process in the examined wetland.

The effects of dexamethasone on post-asphyxial cerebral oxygenation in the preterm fetal sheep

PubMed Central

Lear, Christopher A; Koome, Miriam E; Davidson, Joanne O; Drury, Paul P; Quaedackers, Josine S; Galinsky, Robert; Gunn, Alistair J; Bennet, Laura

2014-01-01

Exposure to clinical doses of the glucocorticoid dexamethasone increases brain activity and causes seizures in normoxic preterm fetal sheep without causing brain injury. In contrast, the same treatment after asphyxia increased brain injury. We hypothesised that increased injury was in part mediated by a mismatch between oxygen demand and oxygen supply. In preterm fetal sheep at 0.7 gestation we measured cerebral oxygenation using near-infrared spectroscopy, electroencephalographic (EEG) activity, and carotid blood flow (CaBF) from 24 h before until 72 h after asphyxia induced by 25 min of umbilical cord occlusion. Ewes received dexamethasone intramuscularly (12 mg 3 ml–1) or saline 15 min after the end of asphyxia. Fetuses were studied for 3 days after occlusion. During the first 6 h of recovery after asphyxia, dexamethasone treatment was associated with a significantly greater fall in CaBF (P < 0.05), increased carotid vascular resistance (P < 0.001) and a greater fall in cerebral oxygenation as measured by the difference between oxygenated and deoxygenated haemoglobin (delta haemoglobin; P < 0.05). EEG activity was similarly suppressed in both groups. From 6 to 10 h onward, dexamethasone treatment was associated with a return of CaBF to saline control levels, increased EEG power (P < 0.005), greater epileptiform transient activity (P < 0.001), increased oxidised cytochrome oxidase (P < 0.05) and an attenuated increase in [delta haemoglobin] (P < 0.05). In conclusion, dexamethasone treatment after asphyxia is associated with greater hypoperfusion in the critical latent phase, leading to impaired intracerebral oxygenation that may exacerbate neural injury after asphyxia. PMID:25384775

Structure-activity relationships for the impact of selected isothiazol-3-one biocides on glutathione metabolism and glutathione reductase of the human liver cell line Hep G2.

PubMed

Arning, Jürgen; Dringen, Ralf; Schmidt, Maike; Thiessen, Anette; Stolte, Stefan; Matzke, Marianne; Bottin-Weber, Ulrike; Caesar-Geertz, Birgit; Jastorff, Bernd; Ranke, Johannes

2008-04-18

To investigate the toxic mode of action of isothiazol-3-one biocides the four compounds N-methylisothiazol-3-one (MIT), 5-chloro-N-methylisothiazol-3-one (CIT), N-octylisothiazol-3-one (OIT) and 4,5-dichloro-N-octylisothiazol-3-one (DCOIT) were purified and tested as single chemical entities for their effects on the human hepatoblastoma cell line Hep G2 and on isolated and cellular glutathione reductase GR). The two chlorinated substances CIT and DCOIT significantly decreased the amount of total cellular glutathione (GSx) in a dose and time dependent manner. Concomitantly, an increase in the level of oxidised glutathione (GSSG) was observed. The resulting shift in the GSH/GSSG ratio entailing the breakdown of the cellular thiol reduction potential was accompanied by necrotic morphological changes like swelling of the plasma membrane and subsequent lysis of the cells. Additionally, CIT and DCOIT were found to inhibit cellular GR in the cells in a concentration dependent manner. The T-SAR-based (thinking in terms of structure-activity relationships) comparison of the chlorine-substituted structures CIT and DCOIT with their non-chlorinated and less active analogues MIT and OIT identified the chlorine substituents and the resulting reaction mechanisms to be the key structural mediators of the observed toxic effects. Furthermore, differences in the activity of both chlorinated substances could be explained using the T-SAR approach to link the lipophilicity and the intrinsic glutathione-reactivity of the compounds to the expected target site concentrations inside the cells.

Lithologically controlled invisible gold, Yukon, Canada

NASA Astrophysics Data System (ADS)

MacKenzie, Doug; Craw, Dave; Finnigan, Craig

2015-02-01

The newly discovered Cretaceous Coffee orogenic gold deposit (>4 Moz resource) consists of an extensive oxidised zone developed on primary sulphidic rock. The primary mineralised rock is characterised by invisible gold in arsenian pyrite that has replaced biotite in selected host rocks. The deposit has a cryptic surface expression and is an example of an extremely subtle exploration target. Hydrothermal emplacement was controlled by extensional fractures, with breccias, but most mineralisation was focused on biotite-bearing granitic gneiss, metasedimentary gneisses, and younger biotite granite. Fine-grained (<0.1 mm) arsenian pyrite replaced biotite along mineral cleavage planes and followed biotite-rich metamorphic and post-metamorphic structural fabrics. Arsenian pyrite also formed overgrowths on earlier coarse-grained (up to 2 mm) barren hydrothermal pyrite. Arsenian pyrite is concentrically zoned on the 1-10-μm scale with respect to As, Sb, and Au contents and typically contains ˜5 wt% As, ˜500 mg/kg Sb, and ˜500 mg/kg Au, in solid solution. Biotite replacement was accompanied by sericitisation, silicification, and ankerite impregnation. Hydrothermal alteration involved dilution and localised depletion of K, Na, and Al in silicified host rocks, but most Ca, Mg, and Fe concentrations remained broadly constant. Magnesium-rich ultramafic host rocks were only weakly mineralised with auriferous arsenian pyrite and have fuchsite and magnesite alteration. Near-surface oxidation has liberated nanoparticulate and microparticulate supergene gold, which remains essentially invisible. Varying degrees of oxidation extend as deep as 250 m below the present subdued topographic surface, well beyond the present vadose zone, and this deep oxidation may have occurred during post-mineralisation uplift and erosion in the Cretaceous. Oxidation has leached some As from the surficial mineralised rocks, decreasing the geochemical signal, which is also obscured by the localised presence of high background As (up to 100 mg/kg) in metasedimentary quartzites in the region. Antimony provides more reliable soil anomalies than As, but most Sb anomalies are <100 mg/kg. The persistence of invisible gold into the extensive supergene zone, with little gold particle size enhancement, has ensured that no placer deposits have formed in nearby streams, further restricting the surface footprint and Au dispersal halo of this subtle exploration target.

Label-free detection of glycoproteins by the lectin biosensor down to attomolar level using gold nanoparticles

PubMed Central

Bertok, Tomas; Sediva, Alena; Katrlik, Jaroslav; Gemeiner, Pavol; Mikula, Milan; Nosko, Martin; Tkac, Jan

2016-01-01

We present here an ultrasensitive electrochemical biosensor based on a lectin biorecognition capable to detect concentrations of glycoproteins down to attomolar (aM) level by investigation of changes in the charge transfer resistance (Rct) using electrochemical impedance spectroscopy (EIS). On polycrystalline gold modified by an aminoalkanethiol linker layer, gold nanoparticles were attached. A Sambucus nigra agglutinin was covalently immobilised on a mixed self-assembled monolayer formed on gold nanoparticles and finally, the biosensor surface was blocked by poly(vinylalcohol). The lectin biosensor was applied for detection of sialic acid containing glycoproteins fetuin and asialofetuin. Building of a biosensing interface was carefully characterised by a broad range of techniques such as electrochemistry, EIS, atomic force microscopy, scanning electron microscopy and surface plasmon resonance with the best performance of the biosensor achieved by application of HS-(CH2)11-NH2 linker and gold nanoparticles with a diameter of 20 nm. The lectin biosensor responded to an addition of fetuin (8.7% of sialic acid) with sensitivity of (338 ± 11) Ω decade-1 and to asialofetuin (≤ 0.5% of sialic acid) with sensitivity of (109 ± 10) Ω decade-1 with a blank experiment with oxidised asialofetuin (without recognisable sialic acid) revealing sensitivity of detection of (79 ± 13) Ω decade-1. These results suggest the lectin biosensor responded to changes in the glycan amount in a quantitative way with a successful validation by a lectin microarray. Such a biosensor device has a great potential to be employed in early biomedical diagnostics of diseases such as arthritis or cancer, which are connected to aberrant glycosylation of protein biomarkers in biological fluids. PMID:23601864

Microbial methanol uptake in northeast Atlantic waters

PubMed Central

Dixon, Joanna L; Beale, Rachael; Nightingale, Philip D

2011-01-01

Methanol is the predominant oxygenated volatile organic compound in the troposphere, where it can significantly influence the oxidising capacity of the atmosphere. However, we do not understand which processes control oceanic concentrations, and hence, whether the oceans are a source or a sink to the atmosphere. We report the first methanol loss rates in seawater by demonstrating that 14C-labelled methanol can be used to determine microbial uptake into particulate biomass, and oxidation to 14CO2. We have found that methanol is used predominantly as a microbial energy source, but also demonstrated its use as a carbon source. We report biological methanol oxidation rates between 2.1 and 8.4 nmol l−1 day−1 in surface seawater of the northeast Atlantic. Kinetic experiments predict a Vmax of up to 29 nmol l−1 day−1, with a high affinity Km constant of 9.3 n in more productive coastal waters. We report surface concentrations of methanol in the western English channel of 97±8 n (n=4) between May and June 2010, and for the wider temperate North Atlantic waters of 70±13 n (n=6). The biological turnover time of methanol has been estimated between 7 and 33 days, although kinetic experiments suggest a 7-day turnover in more productive shelf waters. Methanol uptake rates into microbial particles significantly correlated with bacterial and phytoplankton parameters, suggesting that it could be used as a carbon source by some bacteria and possibly some mixotrophic eukaryotes. Our results provide the first methanol loss rates from seawater, which will improve the understanding of the global methanol budget. PMID:21068775

Immobilisation of enzymes on poly(aniline)-poly(anion) composite films. Preparation of bioanodes for biofuel cell applications.

PubMed

Simon, Evelyne; Halliwell, Catherine M; Toh, Chee Seng; Cass, Anthony E G; Bartlett, Philip N

2002-01-01

Immobilisation of enzymes is important for applications such as biosensors or biofuel cells. A poly(histidine) tag had been introduced on the C terminus of a lactate dehydrogenase enzyme. This mutant enzyme was then immobilised onto poly(aniline) (PANi)-poly(anion) composite films, PANi-poly(vinylsulfonate) (PVS) or PANi-poly(acrylate) (PAA). The NADH produced by the immobilised enzyme in the presence of beta-nicotinamide adenine dinucleotide (NAD(+)) and lactate is oxidised at the poly(aniline)-coated electrode at 0.05 to 0.1 V vs. saturated calomel electrode (SCE) at 35 degrees C.

Disulphide bond exchange inhibited by air - kinetic and thermodynamic products in a library of macrocyclic cysteine derivatives.

PubMed

Cholewiak, Agnieszka; Dobrzycki, Łukasz; Jurczak, Janusz; Ulatowski, Filip

2018-04-04

In this paper we present the synthesis and reactivity of dithiols comprising of two cysteine moieties attached to a dipicolinic acid core. Oxidation of these thiols provides oligomeric macrocycles. Monomers with 13-membered rings are kinetic products which are, however, strained and readily transform into higher oligomers under basic conditions or elevated temperature via a disulphide exchange reaction. Dimers, which are the most stable thermodynamic products, equilibrate only under inert conditions with thiolate as a catalyst. Under aerobic conditions, the thiols are oxidised before the equilibrium is reached.

Electrochemical properties and structures of the mixed-valence lithium cuprates Li 3Cu 2O 4 and Li 2NaCu 2O 4

NASA Astrophysics Data System (ADS)

Raekelboom, E. A.; Hector, A. L.; Weller, M. T.; Owen, J. R.

The electrochemical performances of Li 3Cu 2O 4 and Li 2NaCu 2O 4 as cathode materials in lithium coin type batteries have been studied. In Li 3Cu 2O 4, the copper was oxidised to the III level when cycling. The replacement of the lithium by the sodium ions in the octahedral sites in Li 2NaCu 2O 4 might have an effect on the pathway of the lithium ions during the (de)intercalations.

TRANC - a novel fast-response converter to measure total reactive atmospheric nitrogen

NASA Astrophysics Data System (ADS)

Marx, O.; Brümmer, C.; Ammann, C.; Wolff, V.; Freibauer, A.

2011-12-01

The input and loss of plant available nitrogen (N) from/to the atmosphere can be an important factor for the productivity of ecosystems and thus for its carbon and greenhouse gas exchange. We present a novel converter for the measurement of total reactive nitrogen (TRANC: Total Reactive Atmospheric Nitrogen Converter), which offers the opportunity to quantify the sum of all airborne reactive nitrogen (Nr) compounds in high time resolution. The basic concept of the TRANC is the full conversion of total Nr to nitrogen monoxide (NO) within two reaction steps. Initially, reduced N compounds are being oxidised, and oxidised N compounds are thermally converted to lower oxidation states. Particulate N is being sublimated and oxidised or reduced afterwards. In a second step, remaining higher N oxides or those originated in the first step are catalytically converted to NO with carbon monoxide used as reduction gas. The converter is combined with a fast response chemiluminescence detector (CLD) for NO analysis and its performance was tested for the most relevant gaseous and particulate Nr species under both laboratory and field conditions. Recovery rates during laboratory tests for NH3 and NO2 were found to be 95 and 99%, respectively, and 97% when the two gases were combined. In-field longterm stability over an 11-month period was approved by a value of 91% for NO2. Effective conversion was also found for ammonium and nitrate containing particles. The recovery rate of total ambient Nr was tested against the sum of individual measurements of NH3, HNO3, HONO, NH4+, NO3-, and NOx using a combination of different well-established devices. The results show that the TRANC-CLD system precisely captures fluctuations in Nr concentrations and also matches the sum of all Nr compounds measured by the different single techniques. The TRANC features a specific design with very short distance between the sample air inlet and the place where the thermal and catalytic conversions to NO occur. This assures a short residence time of the sample air inside the instrument, and minimises wall sorption problems of water soluble compounds. The fast response time (half-value periods of 0.30 s were found during concentration step changes) and high accuracy in capturing the dominant Nr species enables the converter to be used in an eddy covariance setup. Although a source attribution of specific Nr compounds is not possible, the TRANC is a new reliable tool for permanent measurements of the net Nr flux between ecosystem and atmosphere at a relatively low maintenance and reasonable cost level allowing for diurnal, seasonal and annual investigations.

TRANC - a novel fast-response converter to measure total reactive atmospheric nitrogen

NASA Astrophysics Data System (ADS)

Marx, O.; Brümmer, C.; Ammann, C.; Wolff, V.; Freibauer, A.

2012-05-01

The input and loss of plant available nitrogen (reactive nitrogen: Nr) from/to the atmosphere can be an important factor for the productivity of ecosystems and thus for its carbon and greenhouse gas exchange. We present a novel converter for reactive nitrogen (TRANC: Total Reactive Atmospheric Nitrogen Converter), which offers the opportunity to quantify the sum of all airborne reactive nitrogen compounds (∑Nr) in high time resolution. The basic concept of the TRANC is the full conversion of all Nr to nitrogen monoxide (NO) within two reaction steps. Initially, reduced Nr compounds are being oxidised, and oxidised Nr compounds are thermally converted to lower oxidation states. Particulate Nr is being sublimated and oxidised or reduced afterwards. In a second step, remaining higher nitrogen oxides or those generated in the first step are catalytically converted to NO with carbon monoxide used as reduction gas. The converter is combined with a fast response chemiluminescence detector (CLD) for NO analysis and its performance was tested for the most relevant gaseous and particulate Nr species under both laboratory and field conditions. Recovery rates during laboratory tests for NH3 and NO2 were found to be 95 and 99%, respectively, and 97% when the two gases were combined. In-field longterm stability over an 11-month period was approved by a value of 91% for NO2. Effective conversion was also found for ammonium and nitrate containing particles. The recovery rate of total ambient Nr was tested against the sum of individual measurements of NH3, HNO3, HONO, NH4+, NO3-, and NOx using a combination of different well-established devices. The results show that the TRANC-CLD system precisely captures fluctuations in ∑Nr concentrations and also matches the sum of all individual Nr compounds measured by the different single techniques. The TRANC features a specific design with very short distance between the sample air inlet and the place where the thermal and catalytic conversions to NO occur. This assures a short residence time of the sample air inside the instrument, and minimises wall sorption problems of water soluble compounds. The fast response time (e-folding times of 0.30 to 0.35 s were found during concentration step changes) and high accuracy in capturing the dominant Nr species enables the converter to be used in an eddy covariance setup. Although a source attribution of specific Nr compounds is not possible, the TRANC is a new reliable tool for permanent measurements of the net ∑Nr flux between ecosystem and atmosphere at a relatively low maintenance and reasonable cost level allowing for diurnal, seasonal and annual investigations.

The geological and microbiological controls on the enrichment of Se and Te in sedimentary rocks

NASA Astrophysics Data System (ADS)

Bullock, Liam; Parnell, John; Armstrong, Joseph; Boyce, Adrian; Perez, Magali

2017-04-01

Selenium (Se) and tellurium (Te) have become elements of high interest, mainly due to their photovoltaic and photoconductive properties, and can contaminate local soils and groundwater systems during mobilisation. Due to their economic and environmental significance, it is important to understand the processes that lead to Se- and Te-enrichment in sediments. The distribution of Se and Te in sedimentary environments is primarily a function of redox conditions, and may be transported and concentrated by the movement of reduced fluids through oxidised strata. Se and Te concentrations have been measured in a suite of late Neoproterozoic Gwna Group black shales (UK) and uranium red bed (roll-front) samples (USA). Due to the chemical affinity of Se and sulphur (S), variations in the S isotopic composition of pyrite have also been measured in order to provide insights into their origin. Scanning electron microscopy of pyrite in the black shales shows abundant inclusions of the lead selenide mineral clausthalite. The data for the black shale samples show marked enrichment in Te and Se relative to crustal mean and several hundreds of other samples processed through our laboratory. While Se levels in sulphidic black shales are typically below 5 ppm, the measured values of up to 116 ppm are remarkable. The Se enrichment in roll-fronts (up to 168 ppm) is restricted to a narrow band of alteration at the interface between the barren oxidised core, and the highly mineralised reduced nose of the front. Te is depleted in roll-fronts with respect to the continental crust and other geological settings and deposits. S isotope compositions for pyrite in both the black shales and roll-fronts are very light and indicate precipitation by microbial sulphate reduction, suggesting that Se was microbially sequestered. Results show that Gwna Group black shales and U.S roll-front deposits contain marked elemental enrichments (particularly Se content). In Gwna Group black shales, Se and Te were sequestered out of seawater into pyritic shales at a higher rate than into crusts. Se enrichment in roll-fronts relates to the initial mobilisation of trace elements in oxidised conditions, and later precipitation downgradient in reduced conditions. Results highlight the potential for sedimentary types of Se- and Te-bearing deposits. The enrichment of elements of high value for future technologies in sedimentary rocks deserve careful assessment for potential future resources, and should be monitored during exploration and mobilisation due to the potential contamination effects. This work forms part of the NERC-funded 'Security of Supply of Mineral Resources' project, which aims to detail the science needed to sustain the security of supply of strategic minerals in a changing environment.

PCDD/F catalysis by metal chlorides and oxides.

PubMed

Zhang, Mengmei; Yang, Jie; Buekens, Alfons; Olie, Kees; Li, Xiaodong

2016-09-01

Model fly ash (MFA) samples were composed of silica, sodium chloride, and activated carbon, and doped with metal (0.1 wt% Cu, Cr, Ni, Zn and Cd) chloride or oxide. Each sample was de novo tested at 350 °C for 1 h, in a flow of gas (N2, N2 + 10% O2, +21% O2 or +10% H2) to investigate the effect of metal catalyst and gas composition on PCDD/F formation. Total PCDD/F yield rises rapidly with oxygen content, while the addition of hydrogen inhibits the formation and chlorination of PCDD/F. The amount of PCDD on average rises linearly with the oxygen concentration, while that of PCDF follows a reaction order of about 1/2; thus the PCDF to PCDD ratio drops when more oxygen becomes available. Some samples do not follow this trend. Chlorides are much more active than oxides, yet there are marked differences between individual metals. Principal component analysis (PCA) was applied to study the signatures from all samples, showing their unique specificity and diversity. Each catalyst shows a different signature within its individual homologue groups, demonstrating that these signatures are not thermodynamically controlled. Average congener patterns do not vary considerably with oxygen content changing from oxidising (air) to reducing (nitrogen, hydrogen). Copyright © 2016 Elsevier Ltd. All rights reserved.

Addressing the characterisation challenge to understand catalysis in MOFs: the case of nanoscale Cu supported in NU-1000.

PubMed

Platero-Prats, Ana E; Li, Zhanyong; Gallington, Leighanne C; Peters, Aaron W; Hupp, Joseph T; Farha, Omar K; Chapman, Karena W

2017-09-01

We explore the dynamic structure and reactivity of Cu species supported on NU-1000. By combining pair distribution function (PDF) analysis and difference envelope density (DED) analysis of in situ synchrotron-based X-ray scattering data, we simultaneously probe the local structure of supported Cu-species, their distribution within NU-1000 and distortions of the NU-1000 lattice under conditions relevant to catalysis and catalyst activation. These analyses show that atomic layer deposition (ALD) of Cu in NU-1000 (Cu-AIM) leads to the formation of Cu-oxo clusters within the small pores that connect the triangular and hexagonal channels. Exposure of Cu-AIM to a reducing atmosphere at 200 °C produces metallic Cu 0 of two distinct particle sizes: ∼4 nm nanoparticles and small sub-nanometer clusters. The size of these nanoparticles appears to be constrained by NU-1000 pore dimensions, with evidence of the sub-nanometer clusters being bound within the triangular channels flanked by pyrene rings. This supported Cu 0 -NU-1000 system is catalytically active for gas-phase ethylene hydrogenation. Exposure of the catalyst to oxidative atmosphere re-oxidises the Cu species to a Cu 2 O cuprite phase. The dynamic restructuring of the system in different chemical environments underscores the importance of probing these systems in situ.

Addressing the characterisation challenge to understand catalysis in MOFs: the case of nanoscale Cu supported in NU-1000

DOE PAGES

Platero-Prats, Ana E.; Li, Zhanyong; Gallington, Leighanne C.; ...

2017-04-03

Here, we explore the dynamic structure and reactivity of Cu species supported on NU-1000. By combining pair distribution function (PDF) analysis and difference envelope density (DED) analysis ofin situsynchrotron-based X-ray scattering data, we simultaneously probe the local structure of supported Cu-species, their distribution within NU-1000 and distortions of the NU-1000 lattice under conditions relevant to catalysis and catalyst activation. Our analyses show that atomic layer deposition (ALD) of Cu in NU-1000 (Cu-AIM) leads to the formation of Cu-oxo clusters within the small pores that connect the triangular and hexagonal channels. Exposure of Cu-AIM to a reducing atmosphere at 200 °Cmore » produces metallic Cu 0of two distinct particle sizes: ~4 nm nanoparticles and small sub-nanometer clusters. The size of these nanoparticles appears to be constrained by NU-1000 pore dimensions, with evidence of the sub-nanometer clusters being bound within the triangular channels flanked by pyrene rings. This supported Cu 0–NU-1000 system is catalytically active for gas-phase ethylene hydrogenation. Exposure of the catalyst to oxidative atmosphere re-oxidises the Cu species to a Cu 2O cuprite phase. The dynamic restructuring of the system in different chemical environments underscores the importance of probing these systemsin situ.« less

Effect of resveratrol, tyrosol and beta-sitosterol on oxidised low-density lipoprotein-stimulated oxidative stress, arachidonic acid release and prostaglandin E2 synthesis by RAW 264.7 macrophages.

PubMed

Vivancos, Marta; Moreno, Juan J

2008-06-01

Oxidation of LDL is hypothesised as an early and critical event in atherogenesis. Oxidised LDL (oxLDL) favour the transformation of macrophages into foam cells, an important cell involved in atherosclerosis. Furthermore, oxLDL cause multiple changes in macrophage functions. Thus, oxLDL induces certain genes, suppresses others and alters cell lipid metabolism. Consumption of a Mediterranean diet is associated with a low incidence of atherosclerotic disease, but data about the specific dietary constituents involved and mechanisms conferring cardioprotection are still sparse. The aim of the present study was to determine the effect of representative minor components of wine and olive oil on reactive oxygen species and eicosanoid synthesis induced by oxLDL-stimulated macrophages. We observed that exposure to non-toxic oxLDL concentrations leads to the production of H2O2 by RAW 264.7 macrophages and this effect was reverted by apocynin, a NADPH oxidase inhibitor. Moreover, oxLDL induced arachidonic acid (AA) release, cyclo-oxygenase-2 overexpression and subsequent PGE2 release. We observed that resveratrol and tyrosol revert H2O2 production induced by oxLDL as well as AA release and PGE2 synthesis and that these effects were not as a consequence of these compounds interfering with the oxLDL binding to their receptors. Interestingly, beta-sitosterol presence enhances these polyphenol actions. Thus, we found a synergistic action of polyphenols of olive oil and wine and beta-sitosterol of olive oil led to the modulation of the effects of oxLDL on oxidative stress and PGE2 synthesis.

Membraneless glucose/oxygen enzymatic fuel cells using redox hydrogel films containing carbon nanotubes.

PubMed

MacAodha, Domhnall; Ó Conghaile, Peter; Egan, Brenda; Kavanagh, Paul; Leech, Dónal

2013-07-22

Co-immobilisation of three separate multiple blue copper oxygenases, a Myceliophthora thermophila laccase, a Streptomyces coelicolor laccase and a Myrothecium verrucaria bilirubin oxidase, with an [Os(2,2'-bipyridine)2 (polyvinylimidazole)10Cl](+/2+) redox polymer in the presence of multi-walled carbon nanotubes (MWCNTs) on graphite electrodes results in enzyme electrodes that produce current densities above 0.5 mA cm(-2) for oxygen reduction at an applied potential of 0 V versus Ag/AgCl. Fully enzymatic membraneless fuel cells are assembled with the oxygen-reducing enzyme electrodes connected to glucose-oxidising anodes based on co-immobilisation of glucose oxidase or a flavin adenine dinucleotide-dependent glucose dehydrogenase with an [Os(4,4'-dimethyl-2,2'-bipyridine)2(polyvinylimidazole)10Cl](+/2+) redox polymer in the presence of MWCNTs on graphite electrodes. These fuel cells can produce power densities of up to 145 μW cm(-2) on operation in pH 7.4 phosphate buffer solution at 37 °C containing 150 mM NaCl, 5 mM glucose and 0.12 mM O2. The fuel cells based on Myceliophthora thermophila laccase enzyme electrodes produce the highest power density if combined with glucose oxidase-based anodes. Although the maximum power density of a fuel cell of glucose dehydrogenase and Myceliophthora thermophila laccase enzyme electrodes decreases from 110 μW cm(-2) in buffer to 60 μW cm(-2) on testing in artificial plasma, it provides the highest power output reported to date for a fully enzymatic glucose-oxidising, oxygen-reducing fuel cell in artificial plasma. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Graphene nanoplate-MnO2 composites for supercapacitors: a controllable oxidation approach

NASA Astrophysics Data System (ADS)

Huang, Huajie; Wang, Xin

2011-08-01

Graphene nanoplate-MnO2 composites have been synthesized by oxidising part of the carbon atoms in the framework of graphene nanoplates at ambient temperature. The composites were characterized by means of X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). It was found that the oxidation extent of the carbon atoms in the graphene framework in these composites was dependent on the reaction time, which also influenced their microstructure, morphology and electrochemical properties. Compared with MnO2 nanolamellas, the nanocomposite prepared with a reaction time of 3 h reveals better electrochemical properties as a supercapacitor electrode material.Graphene nanoplate-MnO2 composites have been synthesized by oxidising part of the carbon atoms in the framework of graphene nanoplates at ambient temperature. The composites were characterized by means of X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). It was found that the oxidation extent of the carbon atoms in the graphene framework in these composites was dependent on the reaction time, which also influenced their microstructure, morphology and electrochemical properties. Compared with MnO2 nanolamellas, the nanocomposite prepared with a reaction time of 3 h reveals better electrochemical properties as a supercapacitor electrode material. Electronic supplementary information (ESI) available: Fig. S1, AFM image (5 μm × 5 μm) of graphene nanoplate-MnO2 composite obtained at 3 h; Fig. S2, nitrogen adsorption/desorption isotherm of graphene nanoplate-MnO2 composite obtained at 3 h. See DOI: 10.1039/c1nr10229j

Palaeomagnetism of the loess/palaeosol sequence in Viatovo (NE Bulgaria) in the Danube basin

NASA Astrophysics Data System (ADS)

Jordanova, Diana; Hus, Jozef; Evlogiev, Jordan; Geeraerts, Raoul

2008-03-01

The results of a palaeomagnetic investigation of a 27 m thick loess/palaeosol sequence in Viatovo (NE Bulgaria) are presented in this paper. The sequence consists of topsoil S 0, seven loess horizons (L 1-L 7) and six interbedded palaeosols (S 1-S 6) overlying a red clay (terra rossa) complex. Magnetic viscosity experiments, IRM acquisition, AMS analysis and NRM stepwise alternating and thermal demagnetisation experiments of pilot samples were implemented for precise determination of the characteristic remanence and construction of a reliable magnetostratigraphical scheme. Analysis of IRM acquisition curves using the expectation - maximization algorithm of Heslop et al. [Heslop, D., Dekkers, M., Kruiver, P., van Oorschot, H., 2002. Analysis of isothermal remanent magnetization acquisition curves using the expectation - maximization algorithm. Geophys. J. Int., 148, 58-64] suggests that the best fitting is obtained by three coercivity components. Component 1 corresponds to SD maghemite/magnetite, while component 2 is probably related to the presence of oxidised detrital magnetites. The third component shows varying coercivities depending on the degree of pedogenic alteration of the samples and probably reflects the presence of detrital magnetite grains oxidised at different degree. The relevance of the Viatovo section as a key representative sequence for the loess cover in the Danube basin is confirmed by the presence of geomagnetic polarity changes in the lower part of the sequence. The youngest one recorded in the seventh loess unit L 7 can be identified as corresponding to the Matuyama/Brunhes palaeomagnetic polarity transition. Two normal magnetozones were found in the red clay complex, probably corresponding to the Jaramillo and Olduvai subchronozones of the Matuyama chron.

Oxidised LDL levels decreases after the consumption of ready-to-eat meals supplemented with cocoa extract within a hypocaloric diet.

PubMed

Ibero-Baraibar, I; Abete, I; Navas-Carretero, S; Massis-Zaid, A; Martinez, J A; Zulet, M A

2014-04-01

Cocoa flavanols are recognised by their favourable antioxidant and vascular effects. This study investigates the influence on health of the daily consumption of ready-to-eat meals supplemented with cocoa extract within a hypocaloric diet, on middle-aged overweight/obese subjects. Fifty healthy male and female middle-aged volunteers [57.26 ± 5.24 years and body mass index (BMI) 30.59 ± 2.33 kg/m(2)] were recruited to participate in a 4 week randomised, parallel and double-blind study. After following 3 days on a low-polyphenol diet, 25 volunteers received meals supplemented with 1.4 g of cocoa extract (645.3 mg of polyphenols) and the other 25 participants received control meals, within a 15% energy restriction diet. On the 4th week of intervention individuals in both dietary groups improved (p < 0.05) anthropometric, body composition, blood pressure and blood biochemical measurements. Oxidised LDL cholesterol (oxLDL), showed a higher reduction (p = 0.030) in the cocoa group. Moreover, myeloperoxidase (MPO) levels decreased only in the cocoa supplemented group (p = 0.007). Intercellular Adhesion Molecule-1 (sICAM-1) decreased significantly in both groups, while Vascular Cell Adhesion Molecule-1 (sVCAM-1) did not present differences after the 4 weeks of intervention. Interestingly, cocoa intake showed a different effect by gender, presenting more beneficial effects in men. The consumption of cocoa extract as part of ready-to-eat meals and within a hypocaloric diet improved oxidative status (oxLDL) in middle-aged subjects, being most remarkable in males. Registered at www.clinicaltrials.gov (NCT01596309). Copyright © 2013 Elsevier B.V. All rights reserved.

Intermediate filament structure in fully differentiated (oxidised) trichocyte keratin.

PubMed

Fraser, R D Bruce; Parry, David A D

2017-10-01

For the past 50years there has been considerable debate over the sub-structure of the fully differentiated (oxidised) trichocyte keratin intermediate filament. Depending on the staining and preparative procedures employed, IF observed in transverse section in the transmission electron microscope have varied in appearance between that of a "ring" and a "ring-core" structure, corresponding to the so-called (8+0) and (7+1) protofilament arrangements. In a new analysis of the fine structure of the 1nm equatorial region of the X-ray diffraction pattern of quill we show that the observed pattern is consistent with the (8+0) model and we are also able to assign values to the various parameters. In contrast, we show that the observed X-ray pattern is inconsistent with a (7+1) arrangement. Furthermore, in the (7+1) model steric hindrance would be encountered between the core protofilament and those constituting the ring. The appearance of a central "core" in transverse TEM sections, previously attributed to a central protofilament, is explained in terms of portions of the apolar, disulfide-bonded head and/or tail domains of the trichocyte keratin IF molecules, including the conserved H subdomains, lying along the axis of the IF, thereby decreasing the efficacy of the reducing agents used prior to staining. The H1 subdomain, previously shown to be important in the assembly of epidermal IF molecules at the two- to four-molecule level, is likely to have a similar role for the trichocyte keratins and may form part of a central scaffold on which the molecules assemble into fully functional IF. Copyright © 2017 Elsevier Inc. All rights reserved.

Comparison of the protein-coding genomes of three deep-sea, sulfur-oxidising bacteria: "Candidatus Ruthia magnifica", "Candidatus Vesicomyosocius okutanii" and Thiomicrospira crunogena.

PubMed

McGill, Susan E; Barker, Daniel

2017-07-20

" Candidatus Ruthia magnifica", "Candidatus Vesicomyosocius okutanii" and Thiomicrospira crunogena are all sulfur-oxidising bacteria found in deep-sea vent environments. Recent research suggests that the two symbiotic organisms, "Candidatus R. magnifica" and "Candidatus V. okutanii", may share common ancestry with the autonomously living species T. crunogena. We used comparative genomics to examine the genome-wide protein-coding content of all three species to explore their similarities. In particular, we used the OrthoMCL algorithm to sort proteins into groups of putative orthologs on the basis of sequence similarity. The OrthoMCL inflation parameter was tuned using biological criteria. Using the tuned value, OrthoMCL delimited 1070 protein groups. 63.5% of these groups contained one protein from each species. Two groups contained duplicate protein copies from all three species. 123 groups were unique to T. crunogena and ten groups included multiple copies of T. crunogena proteins but only single copies from the other species. "Candidatus R. magnifica" had one unique group, and had multiple copies in one group where the other species had a single copy. There were no groups unique to "Candidatus V. okutanii", and no groups in which there were multiple "Candidatus V. okutanii" proteins but only single proteins from the other species. Results align with previous suggestions that all three species share a common ancestor. However this is not definitive evidence to make taxonomic conclusions and the possibility of horizontal gene transfer was not investigated. Methodologically, the tuning of the OrthoMCL inflation parameter using biological criteria provides further methods to refine the OrthoMCL procedure.

Evidence of biogeochemical processes in iron duricrust formation

NASA Astrophysics Data System (ADS)

Levett, Alan; Gagen, Emma; Shuster, Jeremiah; Rintoul, Llew; Tobin, Mark; Vongsvivut, Jitraporn; Bambery, Keith; Vasconcelos, Paulo; Southam, Gordon

2016-11-01

Canga is a moderately hard iron-rich duricrust primarily composed of goethite as a result of the weathering of banded iron formations. Canga duricrusts lack a well-developed soil profile and consequently form an innate association with rupestrian plants that may become ferruginised, contributing to canga possessing macroscopic biological features. Examination of polished canga using a field emission scanning electron microscope (FE-SEM) revealed the biological textures associated with canga extended to the sub-millimetre scale in petrographic sections and polished blocks. Laminae that formed by abiotic processes and regions where goethite cements were formed in association with microorganisms were observed in canga. Biological cycling of iron within canga has resulted in two distinct forms of microbial fossilisation: permineralisation of multispecies biofilms and mineralisation of cell envelopes. Goethite permineralised biofilms frequently formed around goethite-rich kaolinite grains in close proximity to goethite bands and were composed of micrometre-scale rod-shaped, cocci and filamentous microfossils. In contrast, the cell envelopes immobilised by authigenic iron oxides were primarily of rod-shaped microorganisms, were not permineralised and occurred in pore spaces within canga. Complete mineralisation of intact rod-shaped casts and the absence of permineralisation suggested mineralised cell envelopes may represent fossilised iron-oxidising bacteria in the canga ecosystem. Replication of these iron-oxidising bacteria appeared to infill the porous regions within canga. Synchrotron-based Fourier transform infrared (FTIR) microspectroscopy demonstrated that organic biomarkers were poorly preserved with only weak bands indicative of aliphatic methylene (CH2) associated with permineralised microbial biofilms. High resolution imaging of microbial fossils in canga that had been etched with oxalic acid supported the poor preservation of organic biomarkers within canga, indicating mineralogical replacement of organic biomarkers.

Metformin preconditioned adipose derived mesenchymal stem cells is a better option for the reversal of diabetes upon transplantation.

PubMed

Shree, Nitya; Bhonde, Ramesh R

2016-12-01

Metformin is used worldwide as an insulin sensitizer. Adipose derived mesenchymal stem cells have shown promising results in the reducing hyperglycemia. We examined whether preconditioning of adipose derived mesenchymal stem cells (ASCs) with metformin could have a better therapeutic value for the reversal of type 2 diabetes. We compared the effect of metformin, ASCs and metformin preconditioned ASCs (MetASCs) in high fat diet induced C57BL/6 mice by injecting the cells intramuscularly only once where as metformin was given at a concentration of 300mg per kg body weight orally daily. Fasting glucose was measured every week for 4 weeks. At the end of the study insulin, triglycerides, IL6 and oxidised LDL were evaluated from the serum. Gene expression studies were performed for muscle (GLUT4) and liver tissues (IL6 and PAI1).There was a remarkable decrease in hyperglycemia within two weeks of injection by MetASCs as compared to metformin and ASCs alone. A significant decrement of hyperinsulinemia, triglyceridemia, serum IL6 and oxidised LDL were observed at the end of the study. Gene expression studies for muscle tissue revealed the drastic upregulation of GLUT4 gene levels in the MetASCs group indicating enhanced glucose uptake in muscle. Liver tissue analysed for the genes involved in inflammation viz. IL6 and PAI1 showed significant downregulation in the MetASCs group as compared to the other groups. This is a first report demonstrating the synergistic effect of metformin preconditioning of ASCs leading to reversal of hyperglycemia, hyperinsulinemia and triglyceridemia. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Near shore groundwater acidification during and after a hydrological drought in the Lower Lakes, South Australia.

PubMed

Leyden, Emily; Cook, Freeman; Hamilton, Benjamin; Zammit, Benjamin; Barnett, Liz; Lush, Ann Marie; Stone, Dylan; Mosley, Luke

2016-06-01

An extreme hydrological drought in the Lower Lakes of the Murray-Darling Basin (Ramsar listed site) resulted in exposure of large areas of lake bed (25% of pre-drought lake area), containing the reduced iron (Fe) sulfide mineral pyrite. The pyrite oxidised and the resulting acidification (pH<4) posed risks of acid and metals entering shallow groundwater and potentially discharging to the remaining lake water body. Piezometer transects were installed at four locations and monitoring of the groundwater levels and quality was undertaken for six years from 2009 (drought) to 2014 (4years post-reinundation). Acidic (pH3-5) groundwater was recorded at three of the four piezometer locations and included sites close to the lake water. The acidic groundwater (0.5-2m below lake bed) at these sites is likely to have originated from the transport of acid from the upper oxidised sediment layer formed during the drought. High soluble metal (Fe, Al, Mn) levels were also recorded at acidic locations. Acidic shallow groundwater has persisted at many sites for over 4years following reinundation post-drought, and is likely due to slow diffusion and limited sulfate reduction. Increases in dissolved Fe and Mn with decreases in redox potential suggest that reductive dissolution of Fe and Mn hydrous oxides and Fe oxy-hydroxysulfate minerals (e.g. jarosite) occurred post-drought. Groundwater hydraulic head gradients were low, indicating there was limited potential for groundwater to discharge to the lake. The hydraulic gradients at all locations were dynamic with complex relationships along the near-shore environment. The results highlight the long lasting and severe effects on groundwater that can occur following hydrological drought in aquatic environments with sulfidic sediments. Crown Copyright © 2016. Published by Elsevier B.V. All rights reserved.

Geochemical characterisation of shallow aquifer sediments of Matlab Upazila, Southeastern Bangladesh — Implications for targeting low-As aquifers

NASA Astrophysics Data System (ADS)

von Brömssen, Mattias; Häller Larsson, Sara; Bhattacharya, Prosun; Hasan, M. Aziz; Ahmed, Kazi Matin; Jakariya, M.; Sikder, Mohiuddin A.; Sracek, Ondra; Bivén, Annelie; Doušová, Barbora; Patriarca, Claudio; Thunvik, Roger; Jacks, Gunnar

2008-07-01

High arsenic (As) concentrations in groundwater pose a serious threat to the health of millions of people in Bangladesh. Reductive dissolution of Fe(III)-oxyhydroxides and release of its adsorbed As is considered to be the principal mechanism responsible for mobilisation of As. The distribution of As is extremely heterogeneous both laterally and vertically. Groundwater abstracted from oxidised reddish sediments, in contrast to greyish reducing sediments, contains significantly lower amount of dissolved arsenic and can be a source of safe water. In order to study the sustainability of that mitigation option, this study describes the lithofacies and genesis of the sediments within 60 m depth and establishes a relationship between aqueous and solid phase geochemistry. Oxalate extractable Fe and Mn contents are higher in the reduced unit than in the oxidised unit, where Fe and Mn are present in more crystalline mineral phases. Equilibrium modelling of saturation indices suggest that the concentrations of dissolved Fe, Mn and PO43--tot in groundwater is influenced by secondary mineral phases in addition to redox processes. Simulating AsIII adsorption on hydroferric oxides using the Diffuse Layer Model and analytical data gave realistic concentrations of dissolved and adsorbed AsIII for the reducing aquifer and we speculate that the presence of high PO43--tot in combination with reductive dissolution results in the high-As groundwater. The study confirms high mobility of As in reducing aquifers with typically dark colour of sediments found in previous studies and thus validates the approach for location of wells used by local drillers based on sediment colour. A more systematic and standardised colour description and similar studies at more locations are necessary for wider application of the approach.

Near shore groundwater acidification during and after a hydrological drought in the Lower Lakes, South Australia

NASA Astrophysics Data System (ADS)

Leyden, Emily; Cook, Freeman; Hamilton, Benjamin; Zammit, Benjamin; Barnett, Liz; Lush, Ann Marie; Stone, Dylan; Mosley, Luke

2016-06-01

An extreme hydrological drought in the Lower Lakes of the Murray-Darling Basin (Ramsar listed site) resulted in exposure of large areas of lake bed (25% of pre-drought lake area), containing the reduced iron (Fe) sulfide mineral pyrite. The pyrite oxidised and the resulting acidification (pH < 4) posed risks of acid and metals entering shallow groundwater and potentially discharging to the remaining lake water body. Piezometer transects were installed at four locations and monitoring of the groundwater levels and quality was undertaken for six years from 2009 (drought) to 2014 (4 years post-reinundation). Acidic (pH 3-5) groundwater was recorded at three of the four piezometer locations and included sites close to the lake water. The acidic groundwater (0.5-2 m below lake bed) at these sites is likely to have originated from the transport of acid from the upper oxidised sediment layer formed during the drought. High soluble metal (Fe, Al, Mn) levels were also recorded at acidic locations. Acidic shallow groundwater has persisted at many sites for over 4 years following reinundation post-drought, and is likely due to slow diffusion and limited sulfate reduction. Increases in dissolved Fe and Mn with decreases in redox potential suggest that reductive dissolution of Fe and Mn hydrous oxides and Fe oxy-hydroxysulfate minerals (e.g. jarosite) occurred post-drought. Groundwater hydraulic head gradients were low, indicating there was limited potential for groundwater to discharge to the lake. The hydraulic gradients at all locations were dynamic with complex relationships along the near-shore environment. The results highlight the long lasting and severe effects on groundwater that can occur following hydrological drought in aquatic environments with sulfidic sediments.

Diversity of life in ocean floor basalt

NASA Astrophysics Data System (ADS)

Thorseth, I. H.; Torsvik, T.; Torsvik, V.; Daae, F. L.; Pedersen, R. B.

2001-12-01

Electron microscopy and biomolecular methods have been used to describe and identify microbial communities inhabiting the glassy margins of ocean floor basalts. The investigated samples were collected from a neovolcanic ridge and from older, sediment-covered lava flows in the rift valley of the Knipovich Ridge at a water depth around 3500 m and an ambient seawater temperature of -0.7°C. Successive stages from incipient microbial colonisation, to well-developed biofilms occur on fracture surfaces in the glassy margins. Observed microbial morphologies are various filamentous, coccoidal, oval, rod-shaped and stalked forms. Etch marks in the fresh glass, with form and size resembling the attached microbes, are common. Precipitation of alteration products around microbes has developed hollow subspherical and filamentous structures. These precipitates are often enriched in Fe and Mn. The presence of branching and twisted stalks that resemble those of the iron-oxidising Gallionella, indicate that reduced iron may be utilised in an energy metabolic process. Analysis of 16S-rRNA gene sequences from microbes present in the rock samples, show that the bacterial population inhabiting these samples cluster within the γ- and ɛ-Proteobacteria and the Cytophaga/Flexibacter/Bacteroides subdivision of the Bacteria, while the Archaea all belong to the Crenarchaeota kingdom. This microbial population appears to be characteristic for the rock and their closest relatives have previously been reported from cold marine waters in the Arctic and Antarctic, deep-sea sediments and hydrothermal environments.

Sulphur and oxygen isotopic characters of dissolved sulphate in groundwater from the Pleistocene aquifer in the southern Jordan Valley (Jericho area, Palestine).

PubMed

Khayat, Saed; Hötzl, Heinz; Geyer, Stefan; Ali, Wasim; Knöller, Kay; Strauch, Gerhard

2006-09-01

Sulphate and chloride concentrations in the shallow Pleistocene aquifer systems in the lower Jordan valley area indicate a general trend of increasing salinity eastward and southward. This study was conducted in one of the important sub-basins feeding the Pleo-Pleistocene aquifer in the Jericho area in the southern part of the valley using S and O isotopes of dissolved sulphate. The results show that sulphate has mainly two contributions to the groundwater. One is the surface seepage, which is present as a salty leachate form with the positive delta34Ssulphate values of primary gypsum in Lisan and Samara formations, and the second is the upwelling saline water which was in contact with a deep secondary gypsum, aragonites and salty rocks and rose up under heavy abstraction with depleted 34S in sulphate and relatively high sulphate and chloride content. The latest was clearly shown in the Arab Project wells to the east that is undergoing a continuous heavy abstraction. The isotopic signatures of S and O in these wells to the east show that this depleted 34S and highly concentrated sulphate might also indicate a dissolved sulphate originating from pyrite oxidation that results from the interaction with a pyrite-rich aquifer, which can well up with salty water under heavy abstraction and is oxidised in the upper aerobic shallow aquifer.

Characterisation of capacitive field-effect sensors with a nanocrystalline-diamond film as transducer material for multi-parameter sensing.

PubMed

Abouzar, M H; Poghossian, A; Razavi, A; Williams, O A; Bijnens, N; Wagner, P; Schöning, M J

2009-01-01

The feasibility of a capacitive field-effect EDIS (electrolyte-diamond-insulator-semiconductor) platform for multi-parameter sensing is demonstrated by realising EDIS sensors with an O-terminated nanocrystalline-diamond (NCD) film as transducer material for the detection of pH and penicillin concentration as well as for the label-free electrical monitoring of adsorption and binding of charged macromolecules, like polyelectrolytes. The NCD films were grown on p-Si-SiO(2) substrates by microwave plasma-enhanced chemical vapour deposition. To obtain O-terminated surfaces, the NCD films were treated in an oxidising medium. The NCD-based field-effect sensors have been characterised by means of constant-capacitance method. The average pH sensitivity of the O-terminated NCD film was 40 mV/pH. A low detection limit of 5 microM and a high penicillin G sensitivity of 65-70 mV/decade has been obtained for an EDIS penicillin biosensor with the adsorptively immobilised enzyme penicillinase. Alternating potential changes, having tendency to decrease with increasing the number of adsorbed polyelectrolyte layers, have been observed after the layer-by-layer deposition of polyelectrolyte multilayers, using positively charged PAH (poly (allylamine hydrochloride)) and a negatively charged PSS (poly (sodium 4-styrene sulfonate)) as a model system. The response mechanism of the developed EDIS sensors is discussed.

Enhanced performance of porphyrin sensitized solar cell based on graphene quantum dots decorated photoanodes

NASA Astrophysics Data System (ADS)

Sehgal, Preeti; Narula, Anudeep Kumar

2018-05-01

Porphyrin sensitized solar cells (PSSC) has been successfully fabricated composed of graphene quantum dots (GQD) functionalized ZnO photoanodes, zinc tetrakis (4-carboxy phenyl)porphyrin (TCPPZn) as sensitizer and polypyrrole coated oxidised multiwalled carbon nanotubes (PPy/OMWCNT) as counter electrode. The effect of the concentration of GQD on the structural, morphological, photophysical and photovoltaic properties of GQD@ZnO, and GQD@ZnO/TCPPZn nanocomposites has also been investigated. Studies indicate that TCPPZn adsorbed on the surface on GQD@ZnO. Hot electron injection mechanism and multiple exciton generation from GQD to ZnO were mainly responsible for the photoexcitation response in PSSC. This study indicates that GQD can play role of sensitizer to some extent. The time decay measurements reveals the evidences of FRET mechanism, and synergistic interaction between GQD and TCPPZn. The Jsc, Voc, PCE of the corresponding PSSC devices enhanced initially and then decreased. Among all the devices fabricated, the PSSC with a 40% amount of GQD (GQD@ZnO/TCPPZn 40%) attains the best performance with the Jsc = 10.1 mA/cm2, Voc = 0.48, PCE = 2.45% FF = 0.507 higher than ZnO@TCPPZn device fabricated without GQD. Overall, this design provides a new concept for the development of photoanodes which derive better efficiency for dye sensitized solar cell (DSSC) and PSSC at economical low cost.

Optimisation of saponin extraction conditions with Camellia sinensis var. assamica seed and its application for a natural detergent.

PubMed

Gong, Wanying; Huang, Yewei; Ji, Aibing; Peng, Wenshu; Liu, Cong; Zeng, Yin; Yang, Ruijuan; Yan, Liang; Wang, Xuanjun; Sheng, Jun

2018-04-01

Camellia sinensis var. assamica seed cake (a by-product of tea-seed oil) is an abundant resource with poor utilisation. C. sinensis var. assamica seed saponin (CSS) is one kind of non-ionic surfactant. In this study, the CSS extraction conditions were optimised by response surface methodology (RSM) and then the CSS detergent was developed. Additionally, the safety and decontamination ability of the developed detergent were evaluated. The optimised extraction conditions were including the extracting temperature of 40.04 °C, extraction time of 4.97 h, ethanol concentration of 64.11% and liquid-solid ratio of 14.57:1 mL g -1 . The formula of the CSS detergent was as follows: 20% crude CSS, 0.3% oxidised tea polyphenols (OTPs), 0.2% nisin, 0.3% sodium dehydroacetate, 0.7% sodium alginate and 0.5% sodium polyacrylate. The LD 50 of the CSS detergent exceeds 14 g kg -1 in mice, indicating the detergent was non-toxic. Both of the emulsifying and the pesticide residues removal abilities of the CSS detergent were significantly stronger than the commercial detergent. A natural tea seed saponin detergent with good safety and decontamination ability was successfully developed. This can make better use of the tea seed cake, thereby creating added value in the tea seed oil industry. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Amyloidosis, Inflammation, and Oxidative Stress in the Heart of an Alkaptonuric Patient

PubMed Central

Ghezzi, Lorenzo; Giorgetti, Giovanna; Viti, Cecilia; Geminiani, Michela; Soldani, Patrizia; Lupetti, Pietro; Benvenuti, Chiara; Perfetto, Federico; Spreafico, Adriano; Santucci, Annalisa

2014-01-01

Background. Alkaptonuria, a rare autosomal recessive metabolic disorder caused by deficiency in homogentisate 1,2-dioxygenase activity, leads to accumulation of oxidised homogentisic acid in cartilage and collagenous structures present in all organs and tissues, especially joints and heart, causing a pigmentation called ochronosis. A secondary amyloidosis is associated with AKU. Here we report a study of an aortic valve from an AKU patient. Results. Congo Red birefringence, Th-T fluorescence, and biochemical assays demonstrated the presence of SAA-amyloid deposits in AKU stenotic aortic valve. Light and electron microscopy assessed the colocalization of ochronotic pigment and SAA-amyloid, the presence of calcified areas in the valve. Immunofluorescence detected lipid peroxidation of the tissue and lymphocyte/macrophage infiltration causing inflammation. High SAA plasma levels and proinflammatory cytokines levels comparable to those from rheumatoid arthritis patients were found in AKU patient. Conclusions. SAA-amyloidosis was present in the aortic valve from an AKU patient and colocalized with ochronotic pigment as well as with tissue calcification, lipid oxidation, macrophages infiltration, cell death, and tissue degeneration. A local HGD expression in human cardiac tissue has also been ascertained suggesting a consequent local production of ochronotic pigment in AKU heart. PMID:24876668

Effects of melatonin on spinal cord injury-induced oxidative damage in mice testis.

PubMed

Yuan, X-C; Wang, P; Li, H-W; Wu, Q-B; Zhang, X-Y; Li, B-W; Xiu, R-J

2017-09-01

This study evaluated the effects of melatonin on spinal cord injury (SCI)-induced oxidative damage in testes. Adult male C57BL/6 mice were randomly divided into sham-, SCI- or melatonin (10 mg/kg, i.p.)-treated SCI groups. To induce SCI, a standard weight-drop method that induced a contusion injury at T10 was used. After 1 week, testicular blood flow velocity was measured using the Laser Doppler Line Scanner. Malondialdehyde (MDA), glutathione (GSH), oxidised glutathione (GSSG) and myeloperoxidase (MPO) were measured in testis homogenates. Microvascular permeability of the testes to Evan's Blue was examined by spectrophotometric and fluorescence microscopic quantitation. The tight junction protein zonula occludens-1 (ZO-1) and occludin in testes were assessed by immunoblot analysis. Melatonin increased the reduced blood flow and decreased SCI-induced permeability of capillaries. MDA levels and MPO activity were elevated in the SCI group compared with shams, which was reversed by melatonin. In contrast, SCI-induced reductions in GSH/GSSG ratio were restored by melatonin. Decreased expression of ZO-1 and occludin was observed, which was attenuated by melatonin. Overall, melatonin treatment protects the testes against oxidative stress damage caused by SCI. © 2016 Blackwell Verlag GmbH.

Effect of carbon nanotube addition on the thermite reaction in the Al/CuO energetic nanocomposite

NASA Astrophysics Data System (ADS)

Sharma, Manjula; Sharma, Vimal

2017-08-01

In this work, the Al/CNT/CuO nano-thermite samples are prepared by ultrasonic mixing with variable CNT content. The morphology of nano-thermites analysed by electron microscopy revealed that the CNTs are dispersed and there are intimate contacts between fuels (Al and CNT) and oxidiser (CuO) constituents of the nano-thermite. Raman spectroscopy technique is used to analyse the structural integrity of the CNTs in the nano-thermite. The thermite reaction characteristics are evaluated by simultaneous thermogravimetric analysis/differential scanning calorimetry technique. The exothermic enthalpy of the Al/CNT/CuO nano-thermite samples increased with increasing CNT content. The effect of Al particle size and Al/Cu molar ratio variation on the thermite reaction enthalpy is also analysed. The ignition temperature of the thermite reaction is also lowered by 71 °C than that of Al/CuO nano-thermite. The activation energy for thermite reaction of Al/CNT/CuO nano-thermite is also lowered by 23% to that of pure Al/CuO. The residues of the nano-thermites after the thermite reaction at 1010 °C are collected and analysed by the X-ray diffraction.

Triterpenoids from Gymnema sylvestre and their pharmacological activities.

PubMed

Fabio, Giovanni Di; Romanucci, Valeria; De Marco, Anna; Zarrelli, Armando

2014-07-28

Because plants are estimated to produce over 200,000 metabolites, research into new natural substances that can be used in the pharmaceutical, agrochemical and agro-industrial production of drugs, biopesticides and food additives has grown in recent years. The global market for plant-derived drugs over the last decade has been estimated to be approximately 30.69 billion USD. A relevant specific example of a plant that is very interesting for its numerous pharmacological properties, which include antidiabetic, anticarcinogenic, and neuroprotective effects is Gymnema sylvestre, used as a medicinal plant in Asia for thousands of years. Its properties are attributed to triterpenoidic saponins. In light of the considerable interest generated in the chemistry and pharmacological properties of G. sylvestre triterpenes and their analogues, we have undertaken this review in an effort to summarise the available literature on these promising bioactive natural products. The review will detail studies on the isolation, chemistry and bioactivity of the triterpenoids, which are presented in the tables. In particular the triterpenoids oxidised at C-23; their isolation, distribution in different parts of the plant, and their NMR spectral data; their names and physico-chemical characterisation; and the biological properties associated with these compounds, with a focus on their potential chemotherapeutic applications.

Factors affecting re-vegetation dynamics of experimentally restored extracted peatland in Estonia.

PubMed

Karofeld, Edgar; Müür, Mari; Vellak, Kai

2016-07-01

Increasing human activity continues to threaten peatlands, and as the area of natural mires declines, our obligation is to restore their ecosystem functions. Several restoration strategies have been developed for restoration of extracted peatlands, including "The moss layer transfer method", which was initiated on the Tässi extracted peatland in central Estonia in May 2012. Three-year study shows that despite the fluctuating water table, rainfall events can compensate for the insufficient moisture for mosses. Total plant cover on the restoration area attained 70 %, of which ~60 % is comprised of target species-Sphagnum mosses. From restoration treatments, spreading of plant fragments had a significant positive effect on the cover of bryophyte and vascular plants. Higher water table combined with higher plant fragments spreading density and stripping of oxidised peat layer affected positively the cover of targeted Sphagnum species. The species composition in the restoration area became similar to that in the donor site in a natural bog. Based on results, it was concluded that the method approved for restoration in North America gives good results also in the restoration of extracted peatland towards re-establishment of bog vegetation under northern European conditions.

Acute administration of 3-nitropropionic acid, a reactive oxygen species generator, boosts ethanol-induced locomotor stimulation. New support for the role of brain catalase in the behavioural effects of ethanol.

PubMed

Manrique, Héctor M; Miquel, Marta; Aragon, Carlos M G

2006-12-01

The antioxidant enzyme catalase by reacting with H(2)O(2), forms the compound known as compound I (catalase-H(2)O(2)). This compound is able to oxidise ethanol to acetaldehyde in the CNS. It has been demonstrated that 3-nitropropionic acid (3-NPA) induces the activity of the brain catalase-H(2)O(2) system. In this study, we tested the effect of 3-NPA on both the brain catalase-H(2)O(2) system and on the acute locomotor effect of ethanol. To find the optimal interval for the 3-NPA-ethanol interaction mice were treated with 3-NPA 0, 45, 90 and 135min before an ethanol injection (2.4mg/kg). In a second study, 3-NPA (0, 15, 30 or 45mg/kg) was administered SC to animals 90min before saline or several doses of ethanol (1.6 or 2.4g/kg), and the open-field behaviour was registered. The specificity of the effect of 3-NPA (45mg/kg) was evaluated on caffeine (10mg/kg IP) and cocaine (4mg/kg)-induced locomotion. The prevention of 3-NPA effects on both ethanol-induced locomotion and brain catalase activity by L-carnitine, a potent antioxidant, was also studied. Nitropropionic acid boosted ethanol-induced locomotion and brain catalase activity after 90min. The effect of 3-NPA was prevented by l-carnitine administration. These results indicate that 3-NPA enhanced ethanol-induced locomotion by increasing the activity of the brain catalase system.

Protective effects of melatonin against thioacetamide-induced liver fibrosis in rats.

PubMed

Czechowska, G; Celinski, K; Korolczuk, A; Wojcicka, G; Dudka, J; Bojarska, A; Reiter, R J

2015-08-01

The aim of this study was to determine the effect of melatonin on thioacetamide (TAA) induced liver fibrosis in rats. The antifibrotic effects of melatonin were assessed by determining activity indirect markers of fibrosis: aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (AP), and proinflammatory cytokines: interleukin 6 (IL-6), interleukin-1beta (IL-1β), tumour necrosis factor alpha (TNF-α), transforming growth factor-beta (TGF-β) and platelet-derived growth factor (PDGF). Parameters of oxidative stress: oxidised glutathione (GSSG), reduced glutathione (GSH) and presaged activity of paraoxonase 1 (PON-1), an antioxidative enzyme were determined. Inflammatory changes and fibrosis extent were evaluated histologically. Experiments were carried out in Wistar rats. Animals were divided into 4 groups: I - controls, water ad libitum for 12 weeks, group II - TAA, 300 mg/L ad libitum for 12 weeks, III - melatonin, 10 mg/kg b.w. intraperitoneally (i.p.) daily for 4 weeks, IV - TAA, 300 mg/L ad libitum for 12 weeks followed by melatonin, 10 mg/kg/b.w. i.p. daily for 4 weeks. Results of serum determinations demonstrated significantly lower activity of AST, ALT and AP in the group receiving TAA followed by melatonin compared to the group receiving only TAA. Immunoenzymatic findings on effect of melatonin on concentration of proinflammatory cytokines confirmed these data. Biochemical examinations in liver homogenates revealed statistically significant improvement (concentration of GSH increases and concentration of GSSG decreases) in animals with TAA-induced liver damage receiving melatonin. Moreover, the activity of PON-1 toward phenyl acetate and paraoxon was increased in liver homogenates and serum in the group receiving TAA followed by melatonin compared to the TAA group without melatonin treatment. Microscopic evaluation disclosed inhibitory effects of melatonin on inflammatory changes and extent of liver fibrosis.

Physical activity below the minimum international recommendations improves oxidative stress, ADMA levels, resting heart rate and small artery endothelial function.

PubMed

Merino, J; Ferré, R; Girona, J; Aguas, D; Cabré, A; Plana, N; Vinuesa, A; Ibarretxe, D; Basora, J; Buixadera, C; Masana, L

2015-01-01

A moderate level of physical activity (PA), such as a daily 30-min walk, reduces cardiovascular risk. There is a lack of evidence about the cardiovascular benefits of PA below this recommendation of minimum PA level. We aimed to study the impact of a lower level of PA on cardiovascular health. Sixty-four overweight/obese men and women were enrolled in a community programme consisting of 4 months of 1h, low-intensity PA two days per week. Before and after the intervention, PA level (METs/h/wk), endogenous antioxidant status (SOD and GPX concentration and activity and oxidised LDL), ADMA concentrations, endothelial function by small artery reactive hyperaemia index (saRHI), and resting heart rate (RHR) were assessed. After the intervention, significant increases in saRHI (P=0.031), SOD and GPX activities, and a decrease in ADMA plasma concentrations, and RHR (P<0.001 for all) were observed. Increases in PA were positively associated with increases in saRHI (r=0.341, P=0.022), GPx (r=0.303, P=0.047) and decreases in RHR (r=-0.302, P=0.047). Multivariate analyses showed that independent predictors of saRHI improvement were an increase in PA (2.65, 95%CI: 1.21-4.01), decrease in RHR (1.91, 95%CI: 1.01-4.98), and an increase in GPx (2.61, 95%CI: 1.16-5.01). In obese and overweight men and women, an increase in PA, even below the minimal international recommendations, improves antioxidant capacity, RHR and peripheral small artery reactivity. Copyright © 2014 Sociedad Española de Arteriosclerosis. Published by Elsevier España. All rights reserved.

Olivine-hosted melt inclusions as an archive of redox heterogeneity in magmatic systems

NASA Astrophysics Data System (ADS)

Hartley, Margaret E.; Shorttle, Oliver; Maclennan, John; Moussallam, Yves; Edmonds, Marie

2017-12-01

The redox state of volcanic products determines their leverage on the oxidation of Earth's oceans and atmosphere, providing a long-term feedback on oxygen accumulation at the planet's surface. An archive of redox conditions in volcanic plumbing systems from a magma's mantle source, through crustal storage, to eruption, is carried in pockets of melt trapped within crystals. While melt inclusions have long been exploited for their capacity to retain information on a magma's history, their permeability to fast-diffusing elements such as hydrogen is now well documented and their retention of initial oxygen fugacities (fO2) could be similarly diffusion-limited. To test this, we have measured Fe3+/ΣFe by micro-XANES spectroscopy in a suite of 65 olivine-hosted melt inclusions and 9 matrix glasses from the AD 1783 Laki eruption, Iceland. This eruption experienced pre-eruptive mixing of chemically diverse magmas, syn-eruptive degassing at the vent, and post-eruptive degassing during lava flow up to 60 km over land, providing an ideal test of whether changes in the fO2 of a magma may be communicated through to its cargo of crystal-hosted melt inclusions. Melt inclusions from rapidly quenched tephra samples have Fe3+/ΣFe of 0.206 ± 0.008 (ΔQFM of +0.7 ± 0.1), with no correlation between their fO2 and degree of trace element enrichment or differentiation. These inclusions preserve the redox conditions of the mixed pre-eruptive Laki magma. When corrected for fractional crystallisation to 10 wt.% MgO, these inclusions record a parental magma [Fe3+/ΣFe](10) of 0.18 (ΔQFM of +0.4), significantly more oxidised than the Fe3+/ΣFe of 0.10 that is often assumed for Icelandic basalt magmas. Melt inclusions from quenched lava selvages are more reduced than those from the tephra, having Fe3+/ΣFe between 0.133 and 0.177 (ΔQFM from -0.4 to +0.4). These inclusions have approached equilibrium with their carrier lava, which has been reduced by sulfur degassing. The progressive re-equilibration of fO2 between inclusions and carrier melts occurs on timescales of hours to days, causing a drop in the sulfur content at sulfide saturation (SCSS) and driving the exsolution of immiscible sulfide globules in the inclusions. Our data demonstrate the roles of magma mixing, progressive re-equilibration, and degassing in redox evolution within magmatic systems, and the open-system nature of melt inclusions to fO2 during these processes. Redox heterogeneity present at the time of inclusion trapping may be overprinted by rapid re-equilibration of melt inclusion fO2 with the external environment, both in the magma chamber and during slow cooling in lava at the surface. This can decouple the melt inclusion archives of fO2, major and trace element chemistry, and mask associations between fO2, magmatic differentiation and mantle source heterogeneity unless the assembly of diverse magmas is rapidly followed by eruption. Our tools for understanding the redox conditions of magmas are thus limited; however, careful reconstruction of pre- and post-eruptive magmatic history has enabled us to confirm the relatively oxidised nature of ocean island-type mantle compared to that of mid-ocean ridge mantle.

Field evaluation of intensive compost application on Cd fractionation and phytoavailability in a mining-contaminated soil.

PubMed

Li, Ming; Mohamed, Ibrahim; Raleve, David; Chen, Wenli; Huang, Qiaoyun

2016-10-01

A field experiment was conducted to investigate the effect of chicken manure compost on the fractionation of cadmium (Cd), soil biological properties and Cd uptake by wheat in a soil affected by mining activities in Hubei province, China. Compost was applied at five levels (0, 27, 54, 108, 216 t ha(-1)), and winter wheat (Triticum aestivum L.) was chosen as an indicator plant. Results showed that the application of compost increased soil pH and the content of total phosphorus and organic matter. Soil biological properties such as microbial biomass carbon, invertase, protease, urease and catalase activities were significantly enhanced by 0.24-3.47 times after compost application. Sequential extraction indicated that compost amendments decreased the acid-extractable Cd by 8.2-37.6 %, while increased the reducible and oxidisable Cd by 9.2-39.5 and 8.2-60.4 %, respectively. The addition of 27-54 t ha(-1) compost reduced Cd content in wheat stems and seeds by 69.6-75.0 % and 10.3-18.4 %, respectively. However, only 25.5-26.5 % reductions in Cd content in wheat stems were observed in 108-216 t ha(-1) compost amendments, and no significant decrease was detected for seeds. This study suggests that although compost is a suitable organic amendment to improve soil fertility and biological activities, the addition of compost should be moderated by an appropriate rate to optimize the use of compost for the reclamation of metal-contaminated soils at field scale.

Occurrence and importance of anaerobic ammonium-oxidising bacteria in vegetable soils.

PubMed

Shen, Li-dong; Wu, Hong-sheng; Gao, Zhi-qiu; Xu, Xiang-hua; Chen, Tie-xi; Liu, Shuai; Cheng, Hai-xiang

2015-07-01

The quantitative importance of anaerobic ammonium oxidation (anammox) has been described in paddy fields, while the presence and importance of anammox in subsurface soil from vegetable fields have not been determined yet. Here, we investigated the occurrence and activity of anammox bacteria in five different types of vegetable fields located in Jiangsu Province, China. Stable isotope experiments confirmed the anammox activity in the examined soils, with the potential rates of 2.1 and 23.2 nmol N2 g(-1) dry soil day(-1), and the anammox accounted for 5.9-20.5% of total soil dinitrogen gas production. It is estimated that a total loss of 7.1-78.2 g N m(-2) year(-1) could be linked to the anammox process in the examined vegetable fields. Phylogenetic analyses showed that multiple co-occurring anammox genera were present in the examined soils, including Candidatus Brocadia, Candidatus Kuenenia, Candidatus Anammoxoglobus and Candidatus Jettenia, and Candidatus Brocadia appeared to be the most common anammox genus. Quantitative PCR further confirmed the presence of anammox bacteria in the examined soils, with the abundance varying from 2.8 × 10(5) to 3.0 × 10(6) copies g(-1) dry soil. Correlation analyses suggested that the soil ammonium concentration had significant influence on the activity and abundance of anammox bacteria in the examined soils. The results of our study showed the presence of diverse anammox bacteria and indicated that the anammox process could serve as an important nitrogen loss pathway in vegetable fields.

Non-enzymatic oxidation of NADH by quinones

NASA Astrophysics Data System (ADS)

Scherbak, Nikolai; Strid, Åke; Eriksson, Leif A.

2005-10-01

Non-enzymatic oxidation of NADH by a large number of different quinones has been explored both theoretically and experimentally. It is concluded that the smaller benzo- and naphtho-quinones are capable of oxidising NADH in aqueous solution, whereas the larger anthraquinone is not. The mechanisms of stepwise electron and proton transfers are explored, and ruled out in favour of direct hydride transfer. For menadione (2-methyl-1,4-naphthoquinone), no reaction is observed experimentally; theoretically we find that there is a very close balance between the energetic cost of hydride removal from NADH and the energy gain of formation of the menadione semiquinone radical anion.

The radiation chemistry of nuclear reactor decontaminating reagents

NASA Astrophysics Data System (ADS)

Sellers, Robin M.

Processes involved in the radiation chemistry of some typical nuclear reactor decontaminating reagents including complexing, reducing and oxidising agents are described. It is concluded that radiation-induced decomposition is only likely to be a problem with dilute formulations, and/or with minor additives such as corrosion inhibitors which are not protected from attack by the other constituents. Addition of a "sacrificial" compound may be necessary to overcome this. The importance of considering loss of function, rather than the decomposition rate of the starting material, is emphasised. Reagents based on low oxidation state metal ions (LOMI) can be regenerated by the radiation field in the presence of formate ion.

Microbial transformations of arsenic in the environment: From soda lakes to aquifers

USGS Publications Warehouse

Lloyd, J.R.; Oremland, R.S.

2006-01-01

Arsenic is a highly toxic element that supports a surprising range of biogeochemical transformations. The biochemical basis of these microbial interactions is described, with an emphasis on energy-yielding redox biotransformations that cycle between the As5+ and As3+ oxidation states. The subsequent impact of As3+-oxidising and As 5+-reducing prokaryotes on the chemistry of selected environments is also described, focusing on soda lakes with naturally high concentrations of the metalloid and on Southeast Asian aquifer sediments, where the microbial reduction of sorbed As5+ and subsequent mobilisation of As 3+ into water abstracted for drinking and irrigation threaten the lives of millions.

An update on oxysterol biochemistry: New discoveries in lipidomics.

PubMed

Griffiths, William J; Wang, Yuqin

2018-02-05

Oxysterols are oxidised derivatives of cholesterol or its precursors post lanosterol. They are intermediates in the biosynthesis of bile acids, steroid hormones and 1,25-dihydroxyvitamin D 3. Although often considered as metabolic intermediates there is a growing body of evidence that many oxysterols are bioactive and their absence or excess may be part of the cause of a disease phenotype. Using global lipidomics approaches oxysterols are underrepresented encouraging the development of targeted approaches. In this article, we discuss recent discoveries important in oxysterol biochemistry and some of the targeted lipidomic approaches used to make these discoveries. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Ferrocene-Boronic Acid-Fructose Binding Based on Dual-Plate Generator-Collector Voltammetry and Square-Wave Voltammetry.

PubMed

Li, Meng; Xu, Su-Ying; Gross, Andrew J; Hammond, Jules L; Estrela, Pedro; Weber, James; Lacina, Karel; James, Tony D; Marken, Frank

2015-06-10

The interaction of ferrocene-boronic acid with fructose is investigated in aqueous 0.1 m phosphate buffer at pH 7, 8 and 9. Two voltammetric methods, based on 1) a dual-plate generator-collector micro-trench electrode (steady state) and 2) a square-wave voltammetry (transient) method, are applied and compared in terms of mechanistic resolution. A combination of experimental data is employed to obtain new insights into the binding rates and the cumulative binding constants for both the reduced ferrocene-boronic acid (pH dependent and weakly binding) and for the oxidised ferrocene-boronic acid (pH independent and strongly binding).

Polyphenols as enzyme inhibitors in different degraded peat soils: Implication for microbial metabolism in rewetted peatlands

NASA Astrophysics Data System (ADS)

Zak, Dominik; Roth, Cyril; Gelbrecht, Jörg; Fenner, Nathalie; Reuter, Hendrik

2015-04-01

Recently, more than 30,000 ha of drained minerotrophic peatlands (= fens) in NE Germany were rewetted to restore their ecological functions. Due to an extended drainage history, a re-establishment of their original state is not expected in the short-term. Elevated concentrations of dissolved organic carbon, ammonium and phosphate have been measured in the soil porewater of the upper degraded peat layers of rewetted fens at levels of one to three orders higher than the values in pristine systems; an indicator of increased microbial activity in the upper degraded soil layers. On the other hand there is evidence that the substrate availability within the degraded peat layer is lowered since the organic matter has formerly been subject to intense decomposition over the decades of drainage and intense agricultural use of the areas. Previously however, it was suggested that inhibition of hydrolytic enzymes by polyphenolic substances is suspended during aeration of peat soils mainly due to the decomposition of the inhibiting polyphenols by oxidising enzymes such as phenol oxidase. Accordingly we hypothesised a lack of enzyme inhibiting polyphenols in degraded peat soils of rewetted fens compared to less decomposed peat of more natural fens. We collected both peat samples at the soil surface (0-20 cm) and fresh roots of dominating vascular plants and mosses (as peat parent material) from five formerly drained rewetted sites and five more natural sites of NE Germany and NW Poland. Less decomposed peat and living roots were used to obtain an internal standard for polyphenol analysis and to run enzyme inhibition tests. For all samples we determined the total phenolic contents and in addition we distinguished between the contents of hydrolysable and condensed tannic substances. From a methodical perspective the advantage of internal standards compared to the commercially available standards cyanidin chloride and tannic acid became apparent. Quantification with cyanidin or tannic acid led to a considerable underestimation (up to 90%) of polyphenolic concentrations in peat soils. As hypothesised we found that highly degraded peat contains far lower levels of total polyphenolics (factor 8) and condensed tannins (factor 50) than less decomposed peat. In addition we detected large differences between different plant species with highest polyphenolic contents for the roots of Carex appropinquata that were more than 10-fold higher than Sphagnum spp. (450 mg/g dry mass vs. 39 mg/g dry mass). Despite these differences, we did not find a significant correlation between enzyme activities and peat degradation state, indicating that there is no simple linear relationship between polyphenolic contents and microbial activity.

Degradation of metaldehyde in water by nanoparticle catalysts and powdered activated carbon.

PubMed

Li, Zhuojun; Kim, Jong Kyu; Chaudhari, Vrushali; Mayadevi, Suseeladevi; Campos, Luiza C

2017-07-01

Metaldehyde, an organic pesticide widely used in the UK, has been detected in drinking water in the UK with a low concentration (<1 μg L -1 ) which is still above the European and UK standard requirements. This paper investigates the efficiency of four materials: powdered activated carbon (PAC) and carbon-doped titanium dioxide nanocatalyst with different concentrations of carbon (C-1.5, C-40, and C-80) for metaldehyde removal from aqueous solutions by adsorption and oxidation via photocatalysis. PAC was found to be the most effective material which showed almost over 90% removal. Adsorption data were well fitted to the Langmuir isotherm model, giving a q m (maximum/saturation adsorption capacity) value of 32.258 mg g -1 and a K L (Langmuir constant) value of 2.013 L mg -1 . In terms of kinetic study, adsorption of metaldehyde by PAC fitted well with a pseudo-second-order equation, giving the adsorption rate constant k 2 value of 0.023 g mg -1  min -1 , implying rapid adsorption. The nanocatalysts were much less effective in oxidising metaldehyde than PAC with the same metaldehyde concentration and 0.2 g L -1 loading concentration of materials under UV light; the maximum removal achieved by carbon-doped titanium dioxide (C-1.5) nanocatalyst was around 15% for a 7.5 ppm metaldehyde solution. Graphical abstract ᅟ.

Electrochemical investigation of [Co4(μ3-O)4(μ-OAc)4(py)4] and peroxides by cyclic voltammetry.

PubMed

Clatworthy, Edwin B; Li, Xiaobo; Masters, Anthony F; Maschmeyer, Thomas

2016-12-13

Two oxidative redox processes of the neutral cobalt(iii) cubane, [Co 4 (μ 3 -O) 4 (μ-OAc) 4 (py) 4 ], were investigated by cyclic voltammetry at a glassy carbon electrode in acetonitrile. In addition to the first quasi-reversible one-electron oxidation at E 1/2 = 0.283 V vs. Fc 0/+ , a second quasi-reversible one-electron oxidation was observed at E 1/2 = 1.44 V vs. Fc 0/+ . Oxidation at this potential does not facilitate water oxidation. In the presence of tert-butylhydroperoxide the peak current of this second oxidation increases, suggesting oxidation of the peroxide by the doubly oxidised cubane.

The use of tungsten as a chronically implanted material.

PubMed

Shah Idil, A; Donaldson, N

2018-04-01

This review paper shows that tungsten should not generally be used as a chronically implanted material. The metal has a long implant history, from neuroscience, vascular medicine, radiography, orthopaedics, prosthodontics, and various other fields, primarily as a result of its high density, radiopacity, tensile strength, and yield point. However, a crucial material criterion for chronically implanted metals is their long-term resistance to corrosion in body fluids, either by inherently noble metallic surfaces, or by protective passivation layers of metal oxide. The latter is often assumed for elemental tungsten, with references to its 'inertness' and 'stability' common in the literature. This review argues that in the body, metallic tungsten fails this criterion, and will eventually dissolve into the soluble hexavalent form W 6+ , typically represented by the orthotungstate [Formula: see text] (monomeric tungstate) anion. This paper outlines the metal's unfavourable corrosion thermodynamics in the human physiological environment, the chemical pathways to either metallic or metal oxide dissolution, the rate-limiting steps, and the corrosion-accelerating effects of reactive oxidising species that the immune system produces post-implantation. Multiple examples of implant corrosion have been reported, with failure by dissolution to varying extents up to total loss, with associated emission of tungstate ions and elevated blood serum levels measured. The possible toxicity of these corrosion products has also been explored. As the field of medical implants grows and designers explore novel solutions to medical implant problems, the authors recommend the use of alternative materials.

A quantum chemical study of the mechanism for proton-coupled electron transfer leading to proton pumping in cytochrome c oxidase

NASA Astrophysics Data System (ADS)

Blomberg, Margareta R. A.; Siegbahn, Per E. M.

2010-10-01

The proton pumping mechanism in cytochrome c oxidase, the terminal enzyme in the respiratory chain, has been investigated using hybrid DFT with large chemical models. In previous studies, a gating mechanism was suggested based on electrostatic interpretations of kinetic experiments. The predictions from that analysis are tested here. The main result is that the suggestion of a positively charged transition state for proton transfer is confirmed, while some other suggestions for the gating are not supported. It is shown that a few critical relative energy values from the earlier studies are reproduced with quite high accuracy using the present model calculations. Examples are the forward barrier for proton transfer from the N-side of the membrane to the pump-loading site when the heme a cofactor is reduced, and the corresponding back leakage barrier when heme a is oxidised. An interesting new finding is an unexpected double-well potential for proton transfer from the N-side to the pump-loading site. In the intermediate between the two transition states found, the proton is bound to PropD on heme a. A possible purpose of this type of potential surface is suggested here. The accuracy of the present values are discussed in terms of their sensitivity to the choice of dielectric constant. Only one energy value, which is not critical for the present mechanism, varies significantly with this choice and is therefore less certain.

Geochemical phase and particle size relationships of metals in urban road dust.

PubMed

Jayarathne, Ayomi; Egodawatta, Prasanna; Ayoko, Godwin A; Goonetilleke, Ashantha

2017-11-01

Detailed knowledge of the processes that metals undergo during dry weather periods whilst deposited on urban surfaces and their environmental significance is essential to predict the potential influence of metals on stormwater quality in order to develop appropriate stormwater pollution mitigation measures. However, very limited research has been undertaken in this area. Accordingly, this study investigated the geochemical phase and particle size relationships of seven metals which are commonly associated with urban road dust, using sequential extraction in order to assess their mobility characteristics. Metals in the sequentially extracted fractions of exchangeable, reducible, oxidisable and residual were found to follow a similar trend for different land uses even though they had variable accumulation loads. The high affinity of Cd and Zn for exchangeable reactions in both, bulk and size-fractionated solid samples confirmed their high mobility, while the significant enrichment of Ni and Cr in the stable residual fraction indicated a low risk of mobility. The study results also confirmed the availability of Cu, Pb and Mn in both, stable and mobile fractions. The fine fraction of solids (<150 μm) and antecedent dry days can be highlighted as important parameters when determining the fate of metals associated with urban road dust. The outcomes from this study are expected to contribute to the development of effective stormwater pollution mitigation strategies by taking into consideration the metal-particulate relationships. Copyright © 2017 Elsevier Ltd. All rights reserved.

Creatinine sensor based on a molecularly imprinted polymer-modified hanging mercury drop electrode.

PubMed

Lakshmi, Dhana; Prasad, Bhim Bali; Sharma, Piyush Sindhu

2006-09-15

Molecularly imprinted polymers (MIP) have been elucidated to work as artificial receptors. In our present study, a MIP was applied as a molecular recognition element to a chemical sensor. We have constructed a creatinine sensor based on a MIP layer selective for creatinine and its differential pulse, cathodic stripping voltammetric detection (DPCSV) on a hanging mercury drop electrode (HMDE). The creatinine sensor was fabricated by the drop coating of dimethylformamide (DMF) solution of a creatinine-imprinted polymer onto the surface of HMDE. The modified-HMDE, preanodised in neutral medium at +0.4V versus Ag/AgCl for 120s, exhibited a marked enhancement in DPCSV current in comparison to the less anodised (

The use of tungsten as a chronically implanted material

NASA Astrophysics Data System (ADS)

Shah Idil, A.; Donaldson, N.

2018-04-01

This review paper shows that tungsten should not generally be used as a chronically implanted material. The metal has a long implant history, from neuroscience, vascular medicine, radiography, orthopaedics, prosthodontics, and various other fields, primarily as a result of its high density, radiopacity, tensile strength, and yield point. However, a crucial material criterion for chronically implanted metals is their long-term resistance to corrosion in body fluids, either by inherently noble metallic surfaces, or by protective passivation layers of metal oxide. The latter is often assumed for elemental tungsten, with references to its ‘inertness’ and ‘stability’ common in the literature. This review argues that in the body, metallic tungsten fails this criterion, and will eventually dissolve into the soluble hexavalent form W6+, typically represented by the orthotungstate WO42- (monomeric tungstate) anion. This paper outlines the metal’s unfavourable corrosion thermodynamics in the human physiological environment, the chemical pathways to either metallic or metal oxide dissolution, the rate-limiting steps, and the corrosion-accelerating effects of reactive oxidising species that the immune system produces post-implantation. Multiple examples of implant corrosion have been reported, with failure by dissolution to varying extents up to total loss, with associated emission of tungstate ions and elevated blood serum levels measured. The possible toxicity of these corrosion products has also been explored. As the field of medical implants grows and designers explore novel solutions to medical implant problems, the authors recommend the use of alternative materials.

Cleaning and disinfection of equipment for gastrointestinal endoscopy. Report of a Working Party of the British Society of Gastroenterology Endoscopy Committee.

PubMed

1998-04-01

Two per cent glutaraldehyde is the most commonly used disinfectant in endoscopy units within the UK. Unfortunately adverse reactions to glutaraldehyde are common among endoscopy personnel and the Health and Safety Commission has recommended substantial reductions in atmospheric levels of glutaraldehyde in order to comply with the Control of Substances Hazardous to Health Regulations, 1994. The Working Party addressed ways of eliminating or minimising exposure to glutaraldehyde in endoscopy units by reviewing alternative disinfectants and the use of automated washer/disinfectors. Alternatives to glutaraldehyde must be at least as microbicidal as glutaraldehyde, non-irritating and compatible with endoscope components and decontamination equipment. Peracetic acid is a highly effective disinfectant and may be a suitable alternative to glutaraldehyde. Peracetic acid has a vinegary-like odour and is claimed to be less irritating than glutaraldehyde. Experience with this agent remains relatively limited and the Working Party recommends that peracetic acid should be used in sealed or exhaust ventilated facilities until further experience is obtained. It is considerably more expensive than glutaraldehyde, is less stable and large volumes have to be stored. It causes cosmetic (but not functional) damage to endoscopes and is not compatible with some washer/ disinfectors. Chlorine dioxide is a powerful oxidising agent and highly effective as a disinfectant. Once activated it must be stored in sealed containers with little head space. Fumes cause irritation and sealed or exhaust ventilated facilities are necessary. The agent may damage some metallic and polymer components of endoscopes and automated washer/disinfectors and compatibility should be established with equipment manufacturers before the agent is used. Other disinfectants such as peroxygen compounds and quaternary ammonium derivatives are less suitable because of unsatisfactory mycobactericidal and/or virucidal activity, or incompatibility with endoscopes and automated washer/disinfectors. Alcohol is effective but, on prolonged contact, is damaging to lens cements. It is also flammable and therefore unsuitable for use in large quantities in automated systems. Superoxidised water (Sterilox) is an electrochemical solution (anolyte) containing a mixture of radicals with strong oxidising properties. It is highly microbicidal when freshly generated, provided items are thoroughly clean and strict generation criteria are met--that is, current, pH, redox potential. It seems to be safe for users and provided field trials substantiate laboratory efficacy tests, and the agent is non-damaging, it too may become an alternative to glutaraldehyde. When 2% glutaraldehyde is used for manual and automated disinfection, 10 minutes' immersion is recommended for endoscopes before the session and between patients. This will destroy vegetative bacteria and viruses (including hepatitis B virus (HBV) and HIV). A five minute contact period is recommended for 0.35% peracetic acid and for chlorine dioxide (1100 ppm av ClO2), but if immersed for 10 minutes sporicidal activity will also be achieved. At the end of each session 20 minutes' immersion in glutaraldehyde or five minutes in peracetic acid or chlorine dioxide is recommended. Microbiological studies show that 20 minutes of exposure to 2% glutaraldehyde destroys most organisms, including Mycobacterium tuberculosis. The Working Party concludes therefore that immersion of the endoscope in 2% glutaraldehyde for 20 minutes is sufficient for endoscopy involving patients with AIDS and other immunodeficiency states or pulmonary tuberculosis. Similarly, 20 minutes' immersion is recommended at the start of the list and between cases for endoscopic retrograde cholangiopancreatography (ERCP) when high level disinfection is required. Cleaning and disinfection of endoscopes should be undertaken by trained staff in a dedicated room. Thorough cleaning with detergent

Methodological constraints in interpreting serum paraoxonase-1 activity measurements: an example from a study in HIV-infected patients.

PubMed

Parra, Sandra; Marsillach, Judit; Aragonès, Gerard; Rull, Anna; Beltrán-Debón, Raúl; Alonso-Villaverde, Carlos; Joven, Jorge; Camps, Jordi

2010-03-25

Paraoxonase-1 (PON1) is an antioxidant enzyme that attenuates the production of the monocyte chemoattractant protein-1 (MCP-1) in vitro. Although oxidation and inflammation are closely related processes, the association between PON1 and MCP-1 has not been completely characterised due, probably, to that the current use of synthetic substrates for PON1 measurement limits the interpretation of the data. In the present study, we explored the relationships between the circulating levels of PON1 and MCP-1 in human immunodeficiency virus-infected patients in relation to the multifunctional capabilities of PON1. We measured selected variables in 227 patients and in a control group of 409 participants. Serum PON1 esterase and lactonase activities were measured as the rates of hydrolysis of paraoxon and of 5-(thiobutyl)-butyrolactone, respectively. Oxidised LDL and MCP-1 concentrations were determined by enzyme-linked immunosorbent assay. High-density lipoproteins cholesterol, apolipoprotein A-I, and C-reactive protein concentrations were measured by standard automated methods. There were significant relationships between PON1 activity and several indices of oxidation and inflammation in control subjects and in infected patients. However, these relationships varied not only with disease status but also on the type of substrate used for PON1 measurement. The present study is a cautionary tale highlighting that results of clinical studies on PON1 may vary depending on the methods used as well as the disease studied. Until more specific methods using physiologically-akin substrates are developed for PON1 measurement, we suggest the simultaneous employment of at least two different substrates in order to improve the reliability of the results obtained.

Carbohydrate availability and exercise training adaptation: too much of a good thing?

PubMed

Bartlett, Jonathan D; Hawley, John A; Morton, James P

2015-01-01

Traditional nutritional approaches to endurance training have typically promoted high carbohydrate (CHO) availability before, during and after training sessions to ensure adequate muscle substrate to meet the demands of high daily training intensities and volumes. However, during the past decade, data from our laboratories and others have demonstrated that deliberately training in conditions of reduced CHO availability can promote training-induced adaptations of human skeletal muscle (i.e. increased maximal mitochondrial enzyme activities and/or mitochondrial content, increased rates of lipid oxidation and, in some instances, improved exercise capacity). Such data have led to the concept of 'training low, but competing high' whereby selected training sessions are completed in conditions of reduced CHO availability (so as to promote training adaptation), but CHO reserves are restored immediately prior to an important competition. The augmented training response observed with training-low strategies is likely regulated by enhanced activation of key cell signalling kinases (e.g. AMPK, p38MAPK), transcription factors (e.g. p53, PPARδ) and transcriptional co-activators (e.g. PGC-1α), such that a co-ordinated up-regulation of both the nuclear and mitochondrial genomes occurs. Although the optimal practical strategies to train low are not currently known, consuming additional caffeine, protein, and practising CHO mouth-rinsing before and/or during training may help to rescue the reduced training intensities that typically occur when 'training low', in addition to preventing protein breakdown and maintaining optimal immune function. Finally, athletes should practise 'train-low' workouts in conjunction with sessions undertaken with normal or high CHO availability so that their capacity to oxidise CHO is not blunted on race day.

Sulforaphane Restores Cellular Glutathione Levels and Reduces Chronic Periodontitis Neutrophil Hyperactivity In Vitro

PubMed Central

Dias, Irundika H. K.; Chapple, Ian L. C.; Milward, Mike; Grant, Melissa M.; Hill, Eric; Brown, James; Griffiths, Helen R.

2013-01-01

The production of high levels of reactive oxygen species by neutrophils is associated with the local and systemic destructive phenotype found in the chronic inflammatory disease periodontitis. In the present study, we investigated the ability of sulforaphane (SFN) to restore cellular glutathione levels and reduce the hyperactivity of circulating neutrophils associated with chronic periodontitis. Using differentiated HL60 cells as a neutrophil model, here we show that generation of extracellular O2 . - by the nicotinamide adenine dinucleotide (NADPH) oxidase complex is increased by intracellular glutathione depletion. This may be attributed to the upregulation of thiol regulated acid sphingomyelinase driven lipid raft formation. Intracellular glutathione was also lower in primary neutrophils from periodontitis patients and, consistent with our previous findings, patients neutrophils were hyper-reactive to stimuli. The activity of nuclear factor erythroid-2-related factor 2 (Nrf2), a master regulator of the antioxidant response, is impaired in circulating neutrophils from chronic periodontitis patients. Although patients’ neutrophils exhibit a low reduced glutathione (GSH)/oxidised glutathione (GSSG) ratio and a higher total Nrf2 level, the DNA-binding activity of nuclear Nrf2 remained unchanged relative to healthy controls and had reduced expression of glutamate cysteine ligase catalytic (GCLC), and modifier (GCLM) subunit mRNAs, compared to periodontally healthy subjects neutrophils. Pre-treatment with SFN increased expression of GCLC and GCM, improved intracellular GSH/GSSG ratios and reduced agonist-activated extracellular O2 . - production in both dHL60 and primary neutrophils from patients with periodontitis and controls. These findings suggest that a deficiency in Nrf2-dependent pathways may underpin susceptibility to hyper-reactivity in circulating primary neutrophils during chronic periodontitis. PMID:23826097

Tetrahydrocannabinols in clinical and forensic toxicology.

PubMed

Kochanowski, Maciej; Kała, Maria

2005-01-01

Cannabinoids are the natural constituents of marihuana (cannabis). The main of them are delta9-tetrahydrocannabinol (9THC)--psychoactive agent, cannabinol (CBN) and cannabidiol (CBD). Cannabis is administered either by smoking or orally. 9THC potency and duration of action as well as its and two of its major metabolites concentrations in organism highly depend on the route of administration. A single active dose of 9THC is estimated on 520 mg. 9THC is rapidly metabolised. It is hydroxylated to an active metabolite, I1 -hydroxy-delta9-tetrahydro-cannabinol (11-OH-THC), then oxidised to an inactive 11-nor-9-carboxy-delta9-tetrahydrocannabinol (THCCOOH), which is conjugated with glucuronic acid and predominantly excreted in the urine. The maximum psychological effect persists for 4-6 h after administration despite of very low 9THC blood concentrations. 9THC plasma concentration declined to values of 2-3 ng/ml during 3-4 h after smoking. Such a low concentration of the active compound in human organism create a demand for use of sensitive analytical methods for detection and determination of 9THC and its metabolites. The most effective techniques for 9THC and related compounds determination in biological material are chromatographic ones (gas and liquid) with mass spectrometric detection and different ionization modes. 9THC and its two metabolites (11-OH-THC and THCCOOH) are present in blood and hair, 9THC in saliva, and THCCOOH in urine. 9THC and related compounds are determined in autopsy material, although deaths by overdose of cannabis are exceptionally rare. Fatalities happen most often after intravenous injection of hashish oil. 9THC and its metabolites determination in different biological materials gives the basis for a wide interpretation of analytical results for clinical and forensic toxicology purposes.

Sulforaphane restores cellular glutathione levels and reduces chronic periodontitis neutrophil hyperactivity in vitro.

PubMed

Dias, Irundika H K; Chapple, Ian L C; Milward, Mike; Grant, Melissa M; Hill, Eric; Brown, James; Griffiths, Helen R

2013-01-01

The production of high levels of reactive oxygen species by neutrophils is associated with the local and systemic destructive phenotype found in the chronic inflammatory disease periodontitis. In the present study, we investigated the ability of sulforaphane (SFN) to restore cellular glutathione levels and reduce the hyperactivity of circulating neutrophils associated with chronic periodontitis. Using differentiated HL60 cells as a neutrophil model, here we show that generation of extracellular O2 (. -) by the nicotinamide adenine dinucleotide (NADPH) oxidase complex is increased by intracellular glutathione depletion. This may be attributed to the upregulation of thiol regulated acid sphingomyelinase driven lipid raft formation. Intracellular glutathione was also lower in primary neutrophils from periodontitis patients and, consistent with our previous findings, patients neutrophils were hyper-reactive to stimuli. The activity of nuclear factor erythroid-2-related factor 2 (Nrf2), a master regulator of the antioxidant response, is impaired in circulating neutrophils from chronic periodontitis patients. Although patients' neutrophils exhibit a low reduced glutathione (GSH)/oxidised glutathione (GSSG) ratio and a higher total Nrf2 level, the DNA-binding activity of nuclear Nrf2 remained unchanged relative to healthy controls and had reduced expression of glutamate cysteine ligase catalytic (GCLC), and modifier (GCLM) subunit mRNAs, compared to periodontally healthy subjects neutrophils. Pre-treatment with SFN increased expression of GCLC and GCM, improved intracellular GSH/GSSG ratios and reduced agonist-activated extracellular O2 (. -) production in both dHL60 and primary neutrophils from patients with periodontitis and controls. These findings suggest that a deficiency in Nrf2-dependent pathways may underpin susceptibility to hyper-reactivity in circulating primary neutrophils during chronic periodontitis.

Control of vascular smooth muscle function by Src-family kinases and reactive oxygen species in health and disease

PubMed Central

MacKay, Charles E; Knock, Greg A

2015-01-01

Abstract Reactive oxygen species (ROS) are now recognised as second messenger molecules that regulate cellular function by reversibly oxidising specific amino acid residues of key target proteins. Amongst these are the Src-family kinases (SrcFKs), a multi-functional group of non-receptor tyrosine kinases highly expressed in vascular smooth muscle (VSM). In this review we examine the evidence supporting a role for ROS-induced SrcFK activity in normal VSM contractile function and in vascular remodelling in cardiovascular disease. VSM contractile responses to G-protein-coupled receptor stimulation, as well as hypoxia in pulmonary artery, are shown to be dependent on both ROS and SrcFK activity. Specific phosphorylation targets are identified amongst those that alter intracellular Ca2+ concentration, including transient receptor potential channels, voltage-gated Ca2+ channels and various types of K+ channels, as well as amongst those that regulate actin cytoskeleton dynamics and myosin phosphatase activity, including focal adhesion kinase, protein tyrosine kinase-2, Janus kinase, other focal adhesion-associated proteins, and Rho guanine nucleotide exchange factors. We also examine a growing weight of evidence in favour of a key role for SrcFKs in multiple pro-proliferative and anti-apoptotic signalling pathways relating to oxidative stress and vascular remodelling, with a particular focus on pulmonary hypertension, including growth-factor receptor transactivation and downstream signalling, hypoxia-inducible factors, positive feedback between SrcFK and STAT3 signalling and positive feedback between SrcFK and NADPH oxidase dependent ROS production. We also discuss evidence for and against the potential therapeutic targeting of SrcFKs in the treatment of pulmonary hypertension. PMID:25384773

Extracorporeal liver assist device to exchange albumin and remove endotoxin in acute liver failure: Results of a pivotal pre-clinical study.

PubMed

Lee, Karla C L; Baker, Luisa A; Stanzani, Giacomo; Alibhai, Hatim; Chang, Yu Mei; Jimenez Palacios, Carolina; Leckie, Pamela J; Giordano, Paola; Priestnall, Simon L; Antoine, Daniel J; Jenkins, Rosalind E; Goldring, Christopher E; Park, B Kevin; Andreola, Fausto; Agarwal, Banwari; Mookerjee, Rajeshwar P; Davies, Nathan A; Jalan, Rajiv

2015-09-01

In acute liver failure, severity of liver injury and clinical progression of disease are in part consequent upon activation of the innate immune system. Endotoxaemia contributes to innate immune system activation and the detoxifying function of albumin, critical to recovery from liver injury, is irreversibly destroyed in acute liver failure. University College London-Liver Dialysis Device is a novel artificial extracorporeal liver assist device, which is used with albumin infusion, to achieve removal and replacement of dysfunctional albumin and reduction in endotoxaemia. We aimed to test the effect of this device on survival in a pig model of acetaminophen-induced acute liver failure. Pigs were randomised to three groups: Acetaminophen plus University College London-Liver Dialysis Device (n=9); Acetaminophen plus Control Device (n=7); and Control plus Control Device (n=4). Device treatment was initiated two h after onset of irreversible acute liver failure. The Liver Dialysis Device resulted in 67% reduced risk of death in acetaminophen-induced acute liver failure compared to Control Device (hazard ratio=0.33, p=0.0439). This was associated with 27% decrease in circulating irreversibly oxidised human non-mercaptalbumin-2 throughout treatment (p=0.046); 54% reduction in overall severity of endotoxaemia (p=0.024); delay in development of vasoplegia and acute lung injury; and delay in systemic activation of the TLR4 signalling pathway. Liver Dialysis Device-associated adverse clinical effects were not seen. The survival benefit and lack of adverse effects would support clinical trials of University College London-Liver Dialysis Device in acute liver failure patients. Copyright © 2015 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.

Redox regulation in metabolic programming and inflammation.

PubMed

Griffiths, Helen R; Gao, Dan; Pararasa, Chathyan

2017-08-01

Energy metabolism and redox state are intrinsically linked. In order to mount an adequate immune response, cells must have an adequate and rapidly available energy resource to migrate to the inflammatory site, to generate reactive oxygen species using NADPH as a cofactor and to engulf bacteria or damaged tissue. The first responder cells of the innate immune response, neutrophils, are largely dependent on glycolysis. Neutrophils are relatively short-lived, dying via apoptosis in the process of bacterial killing through production of hypochlorous acid and release of extracellular NETs. Later on, the most prevalent recruited innate immune cells are monocytes. Their role is to complete a damage limitation exercise initiated by neutrophils and then, as re-programmed M2 macrophages, to resolve the inflammatory event. Almost twenty five years ago, it was noted that macrophages lose their glycolytic capacity and become anti-inflammatory after treatment with corticosteroids. In support of this we now understand that, in contrast to early responders, M2 macrophages are predominantly dependent on oxidative phosphorylation for energy. During early inflammation, polarisation towards M1 macrophages is dependent on NOX2 activation which, via protein tyrosine phosphatase oxidation and AKT activation, increases trafficking of glucose transporters to the membrane and consequently increases glucose uptake for glycolysis. In parallel, mitochondrial efficiency is likely to be compromised via nitrosylation of the electron transport chain. Resolution of inflammation is triggered by encounter with apoptotic membranes exposing oxidised phosphatidylserine that interact with the scavenger receptor, CD36. Downstream of CD36, activation of AMPK and PPARγ elicits mitochondrial biogenesis, arginase expression and a switch towards oxidative phosphorylation in the M2 macrophage. Proinflammatory cytokine production by M2 cells decreases, but anti-inflammatory and wound healing growth factor production is maintained to support restoration of normal function. Copyright © 2017. Published by Elsevier B.V.

Structural and kinetic studies of a novel nerol dehydrogenase from Persicaria minor, a nerol-specific enzyme for citral biosynthesis.

PubMed

Tan, Cheng Seng; Hassan, Maizom; Mohamed Hussein, Zeti Azura; Ismail, Ismanizan; Ho, Kok Lian; Ng, Chyan Leong; Zainal, Zamri

2018-02-01

Geraniol degradation pathway has long been elucidated in microorganisms through bioconversion studies, yet weakly characterised in plants; enzyme with specific nerol-oxidising activity has not been reported. A novel cDNA encodes nerol dehydrogenase (PmNeDH) was isolated from Persicaria minor. The recombinant PmNeDH (rPmNeDH) is a homodimeric enzyme that belongs to MDR (medium-chain dehydrogenases/reductases) superfamily that catalyses the first oxidative step of geraniol degradation pathway in citral biosynthesis. Kinetic analysis revealed that rPmNeDH has a high specificity for allylic primary alcohols with backbone ≤10 carbons. rPmNeDH has ∼3 fold higher affinity towards nerol (cis-3,7-dimethyl-2,6-octadien-1-ol) than its trans-isomer, geraniol. To our knowledge, this is the first alcohol dehydrogenase with higher preference towards nerol, suggesting that nerol can be effective substrate for citral biosynthesis in P. minor. The rPmNeDH crystal structure (1.54 Å) showed high similarity with enzyme structures from MDR superfamily. Structure guided mutation was conducted to describe the relationships between substrate specificity and residue substitutions in the active site. Kinetics analyses of wild-type rPmNeDH and several active site mutants demonstrated that the substrate specificity of rPmNeDH can be altered by changing any selected active site residues (Asp 280 , Leu 294 and Ala 303 ). Interestingly, the L294F, A303F and A303G mutants were able to revamp the substrate preference towards geraniol. Furthermore, mutant that exhibited a broader substrate range was also obtained. This study demonstrates that P. minor may have evolved to contain enzyme that optimally recognise cis-configured nerol as substrate. rPmNeDH structure provides new insights into the substrate specificity and active site plasticity in MDR superfamily. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Long-term oxygen depletion from infiltrating groundwaters: Model development and application to intra-glaciation and glaciation conditions

NASA Astrophysics Data System (ADS)

Sidborn, M.; Neretnieks, I.

2008-08-01

Processes that control the redox conditions in deep groundwaters have been studied. The understanding of such processes in a long-term perspective is important for the safety assessment of a deep geological repository for high-level nuclear waste. An oxidising environment at the depth of the repository would increase the solubility and mobility of many radionuclides, and increase the potential risk for radioactive contamination at the ground surface. Proposed repository concepts also include engineered barriers such as copper canisters, the corrosion of which increases considerably in an oxidising environment compared to prevailing reducing conditions. Swedish granitic rocks are typically relatively sparsely fractured and are best treated as a dual-porosity medium with fast flowing channels through fractures in the rock with a surrounding porous matrix, the pores of which are accessible from the fracture by diffusive transport. Highly simplified problems have been explored with the aim to gain understanding of the underlying transport processes, thermodynamics and chemical reaction kinetics. The degree of complexity is increased successively, and mechanisms and processes identified as of key importance are included in a model framework. For highly complex models, analytical expressions are not fully capable of describing the processes involved, and in such cases the solutions are obtained by numerical calculations. Deep in the rock the main source for reducing capacity is identified as reducing minerals. Such minerals are found inside the porous rock matrix and as infill particles or coatings in fractures in the rock. The model formulation also allows for different flow modes such as flow along discrete fractures in sparsely fractured rocks and along flowpaths in a fracture network. The scavenging of oxygen is exemplified for these cases as well as for more comprehensive applications, including glaciation considerations. Results show that chemical reaction kinetics control the scavenging of oxygen during a relatively short time with respect to the lifetime of the repository. For longer times the scavenging of oxygen is controlled by transport processes in the porous rock matrix. The penetration depth of oxygen along the flowpath depends largely on the hydraulic properties, which may vary significantly between different locations and situations. The results indicate that oxygen, in the absence of easily degradable organic matter, may reach long distances along a flow path during the life-time of the repository (hundreds to thousands of metres in a million years depending on e.g. hydraulic properties of the flow path and the availability of reducing capacity). However, large uncertainties regarding key input parameters exist leading to the conclusion that the results from the model must be treated with caution pending more accurate and validated data. Ongoing and planned experiments are expected to reduce these uncertainties, which are required in order to make more reliable predictions for a safety assessment of a nuclear waste repository.

A novel thermophilic methane-oxidizing bacteria from thermal springs of Uzon volcano caldera, Kamchatka

NASA Astrophysics Data System (ADS)

Dvorianchikova, E.; Kizilova, A.; Kravchenko, I.; Galchenko, V.

2012-04-01

Methane is a radiatively active trace gas, contributing significantly to the greenhouse effect. It is 26 times more efficient in absorbing and re-emitting infrared radiation than carbon dioxide. Methanotrophs play an essential role in the global carbon cycle by oxidizing 50-75% of the biologically produced methane in situ, before it reaches the atmosphere. Methane-oxidizing bacteria are isolated from the various ecosystems and described at present. Their biology, processes of methane oxidation in fresh-water, marsh, soil and marine habitats are investigated quite well. Processes of methane oxidation in places with extreme physical and chemical conditions (high or low , salinity and temperature values) are studied in much smaller degree. Such ecosystems occupy a considerable part of the Earth's surface. The existence of aerobic methanotrophs inhabiting extreme environments has been verified so far by cultivation experiments and direct detection of methane monooxygenase genes specific to almost all aerobic methanotrophs. Thermophilic and thermotolerant methanotrophs have been isolated from such extreme environments and consist of the gammaproteobacterial (type I) genera Methylothermus, Methylocaldum, Methylococcus and the verrucomicrobial genus Methylacidiphilum. Uzon volcano caldera is a unique area, where volcanic processes still happen today. Hydrothermal springs of the area are extreme ecosystems which microbial communities represent considerable scientific interest of fundamental and applied character. A thermophilic aerobic methane-oxidising bacterium was isolated from a sediment sample from a hot spring (56.1; 5.3) of Uzon caldera. Strain S21 was isolated using mineral low salt medium. The headspace gas was composed of CH4, Ar, CO2, and O2 (40:40:15:5). The temperature of cultivation was 50, pH 5.5. Cells of strain S21 in exponential and early-stationary phase were coccoid bacilli, about 1 μm in diameter, and motile with a single polar flagellum. PCR and molecular cloning of a pmoA gene fragment have shown that strain S21 was moderately related to the genus Methylothermus; the closest organism is Methylothermus subterraneus. The further studying of strain S21 will expand our knowledge of this group of organisms, important from the ecological point of view.

Synthesis of non-toxic As and Cr nanoparticles through redox activity of highly flexible layered coordination polymer of Ni(II).

PubMed

Agarwal, Rashmi A

2018-03-09

A simple method for the sequestration of As(III) and Cr(VI) from water has been demonstrated by utilizing a highly flexible porous coordination polymer (PCP) of Ni(II) in its as synthesized form or without solvent removal. This PCP reduces the high toxicity of As(III) and Cr(VI) ions into non-toxic As(0) and Cr/Cr 2 O 3 /CrO 2 (zero, tri and tetravalent) nanoparticles (NPs) within its pores, and this is characterized by powder x-ray diffraction, x-ray photoelectron spectroscopy and high-resolution transmission electron microscopy analysis. The high functionality of this polymer is due to the presence of monodentate carboxylate groups of a benzenetricarboxylate linker, which provide anchoring sites to the metal ions of the metal precursors. Due to the highly oxidising nature of these toxic ions, a redox reaction takes place between the framework metal ions and toxic metal ions, which is explained by an electron paramagnetic resonance study. This is the first report to synthesize non-toxic, as well as useful, NPs of As and Cr from their highly toxic ions within the cavities of a PCP for remediation of the toxic waste stream and contaminated waste water.

Polyethylene oxide-polytetrahydrofurane-PEDOT conducting interpenetrating polymer networks for high speed actuators

NASA Astrophysics Data System (ADS)

Plesse, C.; Khaldi, A.; Wang, Q.; Cattan, E.; Teyssié, D.; Chevrot, C.; Vidal, F.

2011-12-01

In recent years, numerous studies on electro-active polymer (EAP) actuators have been reported. One promising technology is the elaboration of electronic conducting polymer-based actuators with interpenetrating polymer network (IPNs) architecture. In this study, the synthesis and characterisation of conducting IPNs for actuator applications is described. The IPNs are synthesised from polyethylene oxide (PEO) and polytetrahydrofurane (PTHF) networks in which the conducting polymer (poly(3,4-ethylenedioxythiophene)) is incorporated. In a first step, PEO/PTHF IPNs were prepared via an 'in situ' process using poly(ethylene glycol) methacrylate and dimethacrylate and hydroxytelechelic PTHF as starting materials. The IPN mechanical properties were examined by DMA and tensile strength tests. N-ethylmethylimidazolium bis(trifluoromethanesulfonyl)imide (EMITFSI) swollen PEO/PTHF IPNs show ionic conductivities up to 10-3 S cm-1 at 30 °C. In a second step, the conducting IPN actuators were prepared by oxidative polymerisation of 3,4-ethylenedioxithiophene (EDOT) using FeCl3 as an oxidising agent within the PEO/PTHF IPN host matrix. The frequency response performance of the bending conducting IPN actuator was then evaluated. The resulting actuator exhibits a mechanical resonance frequency of up to 125 Hz with 0.75% strain for an applied potential of ± 5 V.

Oxidative stability of fermented meat products.

PubMed

Wójciak, Karolina M; Dolatowski, Zbigniew J

2012-04-02

Meat and meat products, which form a major part of our diet, are very susceptible to quality changes resulting from oxidative processes. Quality of fermented food products depends on the course of various physicochemical and biochemical processes. Oxidation of meat components in raw ripening products may be the result of enzymatic changes occurring as a result of activity of enzymes originating in tissues and microorganisms, as well as lipid peroxidation by free radicals. Primary and secondary products of lipid oxidation are extremely reactive and react with other components of meat, changing their physical and chemical properties. Oxidised proteins take on a yellowish, red through brown hue. Products of lipid and protein degradation create a specific flavour and aroma ; furthermore, toxic substances (such as biogenic amines or new substances) are formed as a result of interactions between meat components, e.g. protein-lipid or protein-protein combinations, as well as transverse bonds in protein structures. Oxidation of meat components in raw ripening products is a particularly difficult process. On the one hand it is essential, since the enzymatic and non-enzymatic lipid oxidation creates flavour and aroma compounds characteristic for ripening products; on the other hand excessive amounts or transformations of those compounds may cause the fermented meat product to become a risk to health.

Regulation of substrate use during the marathon.

PubMed

Spriet, Lawrence L

2007-01-01

The energy required to run a marathon is mainly provided through oxidative phosphorylation in the mitochondria of the active muscles. Small amounts of energy from substrate phosphorylation are also required during transitions and short periods when running speed is increased. The three inputs for adenosine triphosphate production in the mitochondria include oxygen, free adenosine diphosphate and inorganic phosphate, and reducing equivalents. The reducing equivalents are derived from the metabolism of fat and carbohydrate (CHO), which are mobilised from intramuscular stores and also delivered from adipose tissue and liver, respectively. The metabolism of fat and CHO is tightly controlled at several regulatory sites during marathon running. Slower, recreational runners run at 60-65% maximal oxygen uptake (VO(2max)) for approximately 3:45:00 and faster athletes run at 70-75% for approximately 2:45:00. Both groups rely heavily on fat and CHO fuels. However, elite athletes run marathons at speeds requiring between 80% and 90% VO(2max), and finish in times between 2:05:00 and 2:20:00. They are highly adapted to oxidise fat and must do so during training. However, they compete at such high running speeds, that CHO oxidation (also highly adapted) may be the exclusive source of energy while racing. Further work with elite athletes is needed to examine this possibility.

Synthesis of non-toxic As and Cr nanoparticles through redox activity of highly flexible layered coordination polymer of Ni(II)

NASA Astrophysics Data System (ADS)

Agarwal, Rashmi A.

2018-03-01

A simple method for the sequestration of As(III) and Cr(VI) from water has been demonstrated by utilizing a highly flexible porous coordination polymer (PCP) of Ni(II) in its as synthesized form or without solvent removal. This PCP reduces the high toxicity of As(III) and Cr(VI) ions into non-toxic As(0) and Cr/Cr2O3/CrO2 (zero, tri and tetravalent) nanoparticles (NPs) within its pores, and this is characterized by powder x-ray diffraction, x-ray photoelectron spectroscopy and high-resolution transmission electron microscopy analysis. The high functionality of this polymer is due to the presence of monodentate carboxylate groups of a benzenetricarboxylate linker, which provide anchoring sites to the metal ions of the metal precursors. Due to the highly oxidising nature of these toxic ions, a redox reaction takes place between the framework metal ions and toxic metal ions, which is explained by an electron paramagnetic resonance study. This is the first report to synthesize non-toxic, as well as useful, NPs of As and Cr from their highly toxic ions within the cavities of a PCP for remediation of the toxic waste stream and contaminated waste water.

Vogel-Fulcher-Tammann freezing of a thermally fluctuating artificial spin ice probed by x-ray photon correlation spectroscopy

DOE PAGES

Morley, S. A.; Alba Venero, D.; Porro, J. M.; ...

2017-03-16

We report on the crossover from the thermal to the athermal regime of an artificial spin ice formed from a square array of magnetic islands whose lateral size, 30 nm × 70 nm, is small enough that they are dynamic at room temperature.We used resonant magnetic soft x-ray photon correlation spectroscopy as a method to observe the time-time correlations of the fluctuating magnetic configurations of spin ice during cooling, which are found to slow abruptly as a freezing temperature of T 0 = 178 ± 5 K is approached. This slowing is well described by a Vogel-Fulcher-Tammann law, implying thatmore » the frozen state is glassy, with the freezing temperature being commensurate with the strength of magnetostatic interaction energies in the array. The activation temperature, T A = 40 ± 10 K, is much less than that expected from a Stoner-Wohlfarth coherent rotation model. Zerofield- cooled/field-cooled magnetometry reveals a freeing up of fluctuations of states within islands above this temperature, caused by variation in the local anisotropy axes at the oxidised edges. This Vogel-Fulcher-Tammann behavior implies that the system enters a glassy state upon freezing, which is unexpected for a system with a well-defined ground state.« less

Vogel-Fulcher-Tammann freezing of a thermally fluctuating artificial spin ice probed by x-ray photon correlation spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morley, S. A.; Alba Venero, D.; Porro, J. M.

We report on the crossover from the thermal to the athermal regime of an artificial spin ice formed from a square array of magnetic islands whose lateral size, 30 nm × 70 nm, is small enough that they are dynamic at room temperature.We used resonant magnetic soft x-ray photon correlation spectroscopy as a method to observe the time-time correlations of the fluctuating magnetic configurations of spin ice during cooling, which are found to slow abruptly as a freezing temperature of T 0 = 178 ± 5 K is approached. This slowing is well described by a Vogel-Fulcher-Tammann law, implying thatmore » the frozen state is glassy, with the freezing temperature being commensurate with the strength of magnetostatic interaction energies in the array. The activation temperature, T A = 40 ± 10 K, is much less than that expected from a Stoner-Wohlfarth coherent rotation model. Zerofield- cooled/field-cooled magnetometry reveals a freeing up of fluctuations of states within islands above this temperature, caused by variation in the local anisotropy axes at the oxidised edges. This Vogel-Fulcher-Tammann behavior implies that the system enters a glassy state upon freezing, which is unexpected for a system with a well-defined ground state.« less

Bioremediating Oil Spills in Nutrient Poor Ocean Waters Using Fertilized Clay Mineral Flakes: Some Experimental Constraints

PubMed Central

Warr, Laurence N.; Friese, André; Schwarz, Florian; Schauer, Frieder; Portier, Ralph J.; Basirico, Laura M.; Olson, Gregory M.

2013-01-01

Much oil spill research has focused on fertilizing hydrocarbon oxidising bacteria, but a primary limitation is the rapid dilution of additives in open waters. A new technique is presented for bioremediation by adding nutrient amendments to the oil spill using thin filmed minerals comprised largely of Fullers Earth clay. Together with adsorbed N and P fertilizers, filming additives, and organoclay, clay flakes can be engineered to float on seawater, attach to the oil, and slowly release contained nutrients. Our laboratory experiments of microbial activity on weathered source oil from the Deepwater Horizon spill in the Gulf of Mexico show fertilized clay treatment significantly enhanced bacterial respiration and consumption of alkanes compared to untreated oil-in-water conditions and reacted faster than straight fertilization. Whereas a major portion (up to 98%) of the alkane content was removed during the 1 month period of experimentation by fertilized clay flake interaction; the reduced concentration of polyaromatic hydrocarbons was not significantly different from the non-clay bearing samples. Such clay flake treatment could offer a way to more effectively apply the fertilizer to the spill in open nutrient poor waters and thus significantly reduce the extent and duration of marine oil spills, but this method is not expected to impact hydrocarbon toxicity. PMID:23864952

Bioremediating oil spills in nutrient poor ocean waters using fertilized clay mineral flakes: some experimental constraints.

PubMed

Warr, Laurence N; Friese, André; Schwarz, Florian; Schauer, Frieder; Portier, Ralph J; Basirico, Laura M; Olson, Gregory M

2013-01-01

Much oil spill research has focused on fertilizing hydrocarbon oxidising bacteria, but a primary limitation is the rapid dilution of additives in open waters. A new technique is presented for bioremediation by adding nutrient amendments to the oil spill using thin filmed minerals comprised largely of Fullers Earth clay. Together with adsorbed N and P fertilizers, filming additives, and organoclay, clay flakes can be engineered to float on seawater, attach to the oil, and slowly release contained nutrients. Our laboratory experiments of microbial activity on weathered source oil from the Deepwater Horizon spill in the Gulf of Mexico show fertilized clay treatment significantly enhanced bacterial respiration and consumption of alkanes compared to untreated oil-in-water conditions and reacted faster than straight fertilization. Whereas a major portion (up to 98%) of the alkane content was removed during the 1 month period of experimentation by fertilized clay flake interaction; the reduced concentration of polyaromatic hydrocarbons was not significantly different from the non-clay bearing samples. Such clay flake treatment could offer a way to more effectively apply the fertilizer to the spill in open nutrient poor waters and thus significantly reduce the extent and duration of marine oil spills, but this method is not expected to impact hydrocarbon toxicity.

Mantle to surface degassing of carbon- and sulphur-rich alkaline magma at El Hierro, Canary Islands

NASA Astrophysics Data System (ADS)

Longpré, Marc-Antoine; Stix, John; Klügel, Andreas; Shimizu, Nobumichi

2017-02-01

Basaltic volcanoes transfer volatiles from the mantle to the surface of the Earth. The quantification of deep volatile fluxes relies heavily on estimates of the volatile content of primitive magmas, the best archive of which is provided by melt inclusions. Available data from volcanoes producing mafic alkaline lavas in a range of tectonic settings suggest high volatile fluxes, but information remains sparse, particularly for intraplate ocean islands. Here we present measurements of volatile and trace element concentrations, as well as sulphur speciation, in olivine-hosted melt inclusions and matrix glasses from quenched basanite lava balloon samples from the 2011-2012 submarine eruption at El Hierro, Canary Islands. The results reveal remarkably high concentrations of dissolved volatiles and incompatible trace elements in this magma, with ∼80 ppm Nb and up to 3420 ppm CO2, 3.0 wt.% H2O and 5080 ppm S. Reconstructed primitive CO2 contents, considering CO2/Nb systematics and possible CO2 sequestration in shrinkage bubbles, reach weight percent levels, indicating that carbon is a major constituent of Canary Island magmas at depth and that exsolution of a CO2-rich fluid begins in the mantle at pressures in excess of 1 GPa. Correlations between sulphur concentration, sulphur speciation and water content suggest strong reduction of an initially oxidised mantle magma, likely controlled by coupled H2O and S degassing. This late-stage redox change may have triggered sulphide saturation, recorded by globular sulphide inclusions in clinopyroxene and ulvöspinel. The El Hierro basanite thus had a particularly high volatile-carrying capacity and released a minimum of 1.3-2.1 Tg CO2 and 1.8-2.9 Tg S to the environment, causing substantial stress on the local submarine ecosystem. These results highlight the important contribution of alkaline ocean island volcanoes, such as the Canary Islands, to volatile fluxes from the mantle.

Low-temperature Kinetic Studies of OH Radical Reactions Relevant to Planetary Atmospheres

NASA Astrophysics Data System (ADS)

Townsend, T. M.; Antiñolo, M.; Ballesteros, B.; Jimenez, E.; Canosa, A.

2011-05-01

In the solar system, the temperature (T) of the atmosphere of giant planets or their satellites is only several tens of Kelvin (K). The temperature of the tropopause of Titan (satellite of Saturn) and the surface of Mars is 70 K and 210 K, respectively. In the Earth's atmosphere, T decreases from 298 K (surface) to 210 K close to the T-inversion region (tropopause). The principal oxidants in the Earth's lower atmosphere are ozone, the hydroxyl (OH) radical and hydrogen peroxide. A number of critical atmospheric chemical problems depend on the Earth's oxidising capacity, which is essentially the global burden of these oxidants. In the interstellar clouds and circumstellar envelopes, OH radicals have also been detected. As the chemistry of atmospheres is highly influenced by temperature, the knowledge of the T-dependence of the rate coefficients for OH-reactions (k) is the key to understanding the underlying molecular mechanisms. In general, these reactions take place on a short temporal scale. Therefore, a detection technique with high temporal resolution is required. Measurements of k at low temperatures can be achieved by maintaining a thermalised environment using either cryogenic cooling (T>200 K) or supersonic gas expansion with a Laval nozzle (several tens of K). The pulsed laser photolysis technique coupled with laser induced fluorescence detection has been widely used in our laboratory to determine the rate coefficients of OH-reactions with different volatile organic compounds, such as alcohols (1), saturated and unsaturated aliphatic aldehydes (2), linear ketones (3), as a function of temperature (260 350 K). An experimental system based on the CRESU (Cinetique de Reaction en Ecoulement Supersonique Uniforme or Reaction Kinetics in a Uniform Supersonic Flow) technique is currently under construction. This technique will allow the performance of kinetic studies of OH-reactions of astrophysical interest at temperatures lower than 200 K.

Genome-Guided Analysis and Whole Transcriptome Profiling of the Mesophilic Syntrophic Acetate Oxidising Bacterium Syntrophaceticus schinkii

PubMed Central

Manzoor, Shahid; Bongcam-Rudloff, Erik; Schnürer, Anna; Müller, Bettina

2016-01-01

Syntrophaceticus schinkii is a mesophilic, anaerobic bacterium capable of oxidising acetate to CO2 and H2 in intimate association with a methanogenic partner, a syntrophic relationship which operates close to the energetic limits of microbial life. Syntrophaceticus schinkii has been identified as a key organism in engineered methane-producing processes relying on syntrophic acetate oxidation as the main methane-producing pathway. However, due to strict cultivation requirements and difficulties in reconstituting the thermodynamically unfavourable acetate oxidation, the physiology of this functional group is poorly understood. Genome-guided and whole transcriptome analyses performed in the present study provide new insights into habitat adaptation, syntrophic acetate oxidation and energy conservation. The working draft genome of Syntrophaceticus schinkii indicates limited metabolic capacities, with lack of organic nutrient uptake systems, chemotactic machineries, carbon catabolite repression and incomplete biosynthesis pathways. Ech hydrogenase, [FeFe] hydrogenases, [NiFe] hydrogenases, F1F0-ATP synthase and membrane-bound and cytoplasmic formate dehydrogenases were found clearly expressed, whereas Rnf and a predicted oxidoreductase/heterodisulphide reductase complex, both found encoded in the genome, were not expressed under syntrophic growth condition. A transporter sharing similarities to the high-affinity acetate transporters of aceticlastic methanogens was also found expressed, suggesting that Syntrophaceticus schinkii can potentially compete with methanogens for acetate. Acetate oxidation seems to proceed via the Wood-Ljungdahl pathway as all genes involved in this pathway were highly expressed. This study shows that Syntrophaceticus schinkii is a highly specialised, habitat-adapted organism relying on syntrophic acetate oxidation rather than metabolic versatility. By expanding its complement of respiratory complexes, it might overcome limiting bioenergetic barriers, and drive efficient energy conservation from reactions operating close to the thermodynamic equilibrium, which might enable S. schinkii to occupy the same niche as the aceticlastic methanogens. The knowledge gained here will help specify process conditions supporting efficient and robust biogas production and will help identify mechanisms important for the syntrophic lifestyle. PMID:27851830

Inosine Can Increase DNA's Susceptibility to Photo-oxidation by a RuII Complex due to Structural Change in the Minor Groove.

PubMed

Keane, Páraic M; Hall, James P; Poynton, Fergus E; Poulsen, Bjørn C; Gurung, Sarah P; Clark, Ian P; Sazanovich, Igor V; Towrie, Michael; Gunnlaugsson, Thorfinnur; Quinn, Susan J; Cardin, Christine J; Kelly, John M

2017-08-01

Key to the development of DNA-targeting phototherapeutic drugs is determining the interplay between the photoactivity of the drug and its binding preference for a target sequence. For the photo-oxidising lambda-[Ru(TAP) 2 (dppz)] 2+ (Λ-1) (dppz=dipyridophenazine) complex bound to either d{T 1 C 2 G 3 G 4 C 5 G 6 C 7 C 8 G 9 A 10 } 2 (G9) or d{TCGGCGCCIA} 2 (I9), the X-ray crystal structures show the dppz intercalated at the terminal T 1 C 2 ;G 9 A 10 step or T 1 C 2 ;I 9 A 10 step. Thus substitution of the G 9 nucleobase by inosine does not affect intercalation in the solid state although with I9 the dppz is more deeply inserted. In solution it is found that the extent of guanine photo-oxidation, and the rate of back electron-transfer, as determined by pico- and nanosecond time-resolved infrared and transient visible absorption spectroscopy, is enhanced in I9, despite it containing the less oxidisable inosine. This is attributed to the nature of the binding in the minor groove due to the absence of an NH 2 group. Similar behaviour and the same binding site in the crystal are found for d{TTGGCGCCAA} 2 (A9). In solution, we propose that intercalation occurs at the C 2 G 3 ;C 8 I 9 or T 2 G 3 ;C 8 A 9 steps, respectively, with G 3 the likely target for photo-oxidation. This demonstrates how changes in the minor groove (in this case removal of an NH 2 group) can facilitate binding of Ru II dppz complexes and hence influence any sensitised reactions occurring at these sites. No similar enhancement of photooxidation on binding to I9 is found for the delta enantiomer. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Citizen science identifies the effects of nitrogen deposition, climate and tree species on epiphytic lichens across the UK.

PubMed

Welden, N A; Wolseley, P A; Ashmore, M R

2018-01-01

A national citizen survey quantified the abundance of epiphytic lichens that are known to be either sensitive or tolerant to nitrogen (N) deposition. Records were collected across the UK from over 10,000 individual trees of 22 deciduous species. Mean abundance of tolerant and sensitive lichens was related to mean N deposition rates and climatic variables at a 5 km scale, and the response of lichens was compared on the three most common trees (Quercus, Fraxinus and Acer) and by assigning all 22 tree species to three bark pH groups. The abundance of N-sensitive lichens on trunks decreased with increasing total N deposition, while that of N-tolerant lichens increased. The abundance of N-sensitive lichens on trunks was reduced close to a busy road, while the abundance of N-tolerant lichens increased. The abundance of N-tolerant lichen species on trunks was lower on Quercus and other low bark pH species, but the abundance of N-sensitive lichens was similar on different tree species. Lichen abundance relationships with total N deposition did not differ between tree species or bark pH groups. The response of N-sensitive lichens to reduced nitrogen was greater than to oxidised N, and the response of N-tolerant lichens was greater to oxidised N than to reduced N. There were differences in the response of N-sensitive and N-tolerant lichens to rainfall, humidity and temperature. Relationships with N deposition and climatic variables were similar for lichen presence on twigs as for lichen abundance on trunks, but N-sensitive lichens increased, rather than decreased, on twigs of Quercus/low bark pH species. The results demonstrate the unique power of citizen science to detect and quantify the air pollution impacts over a wide geographical range, and specifically to contribute to understanding of lichen responses to different chemical forms of N deposition, local pollution sources and bark chemistry. Copyright © 2017 Elsevier Ltd. All rights reserved.

Identification and distribution of sulfate reducing bacteria and sulphur-oxidising bacteria in northern South China Sea

NASA Astrophysics Data System (ADS)

Mao, S.; Zhu, X.; Guan, H.; Wu, D.; Wu, N.

2015-12-01

Fatty acids are one of the major components in modern marine sediments. It is well known that the saturated short-chain FAs were typically to be from vascular plants, algae, bacteria, and other sources, while the saturated long-chain FAs are the major components found in leaf waxes, suberin, and cutin in terrestrial higher plants. So the lipid biomarkers of fatty acids in Site 4B from Shenhu Area, northern South China Sea were investigated in Recent research supported from the 973 Program (2009CB219506), and the resources of branched fatty acids and monounsaturated fatty acids were mainly discussed. The results reveal that i/a15:0, i/a17:0, 16:1ω5, 18:1ω9 and 10me16:0 are derived from sulfate reducing bacteria (SRB), while 16:1ω7t/c and 18:1ω7 are originated from sulphur-oxidising bacteria (SOB). The biomakers of methanotrophs such as 16:1ω6/8 and 18:1ω6/8 were not detected in the sediments which coincide with more positive carbon isotope values of the fatty acids in the sediments. The stable relationship between SRB and SOB below 97cm in the sediments reflects the relative stable oxidative and reductive depositional environment which may be connected with the sulphur cycle in the sediments, that is carried out as sulfate is reduced to sulfide, and then sulfide is oxidized to sulfate and elemental sulfur, at last elemental sulfur is disproportionated to sulfide and sulfate. The frequently changed relationship of SRB and SOB above 97cm in the sediments indicates intensely changing oxidative and reductive sedimental environment, that may related with diapir structure around Site 4B, which also brings about hydrocarbon seepage leading to increasing biomass at 97cm.

Studies on the electron acceptors of photosystem two

NASA Astrophysics Data System (ADS)

Bowden, Simon John

The differences in temperature dependent behaviour and microwave power saturation characteristics between the g=1.9 and g=1.8 QA -Fe2+ signals are described. The dependence of these behaviourial differences on the presence or absence of bicarbonate is emphasised. By studying the EPR signals of QA-Fe2+, Q-Fe2+, Q-Fe2+TBTQ- and the oxidised non-haem iron I have found that detergent solubilisation of BBY PS2 preparations with the detergent OGP, at pH 6.0, results in loss of bicarbonate binding. New preparations, including a dodecylmaltoside prepared CP47, CP4 3, D1, D2, cytochrome bgsg complex, are described which at pH 7.5 retain native bicarbonate binding. These preparations provide a new system for studies into the "bicarbonate effect" because bicarbonate depletion can now be achieved without displacement by another anion. The new OGP particles have been used to investigate both the split pheophytin signal and the two step redox titration phenomenon associated with this signal. The low potential step of the titration was concluded to be independent of the QA/QA- mid-point potential but was found to be linked to the ability to photoreduce pheophytin; once the low potential component, suggested here to be the fluorescence quencher QL, was reduced, pheophytin photoreduction increased. A model is described to explain the two step titration and, from analysis of the signal splitting in +/- HCO3- samples, a possible structural role for bicarbonate is proposed. I have probed the structure of the PS2 electron acceptor region with the protease trypsin. The QA, iron-semiquinone; oxidised non-haem iron and cytochrome bss, EPR signals were all found to be susceptible to trypsin damage, while oxygen evolution with ferricyanide was enhanced by protease treatment. The protective effect of calcium ions against trypsin damage was demonstrated and a possible Ca2+ binding site in the binding region identified.

Geological factors controlling occurrence and distribution of arsenic in groundwaters from the southern margin of the Duero Basin, Spain.

PubMed

Giménez-Forcada, Elena; Smedley, Pauline L

2014-12-01

Groundwater from springs and boreholes on the southern edge of the Cenozoic Duero Basin (DB) of Spain has concentrations of arsenic (As) which are commonly above the EC drinking-water limit of 10 μg/L and reach observed values up to 241 μg/L. Groundwater compositions within the sedimentary aquifer vary from Ca-HCO3 type, variably affected by evaporation and agricultural pollution at shallow levels, to Na-HCO3 compositions in deeper boreholes of the basin. Groundwater conditions are mainly oxidising, but reducing groundwaters exist in sub-basins within the aquifer, localised flow paths likely being influenced by basement structure. Arsenic concentrations are spatially variable, reaching up to 38 μg/L in springs of the Spanish Central System (SCS) basement aquifer and up to 62 μg/L in springs from the DB. Highest As concentrations are associated with the Na-HCO3 compositions in deep boreholes (200-450 m depth) within the DB. These have high pH values (up to 9.6) which can give rise to associated elevated concentrations of V and U (up to 64 and 30 μg/L, respectively). In the deep borehole waters of the DB, oxidising flows derived from the mineralised igneous-metamorphic basement and discharging via major faults, and are considered the origin of the higher concentrations. Compositions are consistent with desorption of As and other anionic species from metal oxyhydroxides in an oxic environment. Under locally reducing conditions prevalent in some low-flow parts of the DB, an absence of detectable dissolved As is coincident with low or undetectable SO4 concentrations, and consistent with loss via formation of authigenic sulphide minerals. Mitigation measures are needed urgently in this semi-arid region where provision of alternative sources of safe drinking water is logistically difficult and expensive.

Factors controlling charge recombination under dark and light conditions in dye sensitised solar cells.

PubMed

Barnes, Piers R F; Anderson, Assaf Y; Juozapavicius, Mindaugas; Liu, Lingxuan; Li, Xiaoe; Palomares, Emilio; Forneli, Amparo; O'Regan, Brian C

2011-02-28

A simple and powerful approach for assessing the recombination losses in dye sensitised solar cells (DSSCs) across the current voltage curve (j-V) as a function of TiO(2) electron concentration (n) is demonstrated. The total flux of electrons recombining with iodine species in the electrolyte and oxidised dye molecules can be thought of as a recombination current density, defined as j(rec) = j(inj)-j where j(inj) is the current of electrons injected from optically excited dye states and j is the current density collected at cell voltage (V). The electron concentration at any given operating conditions is determined by charge extraction. This allows comparison of factors influencing electron recombination rates at matched n. We show that j(rec) is typically 2-3 times higher under 1 sun equivalent illumination (j(inj) > 0) relative to dark (j(inj) = 0) conditions. This difference was increased by increasing light intensity, electrolyte iodine concentration and electrolyte solvent viscosity. The difference was reduced by increasing the electrolyte iodide concentration and increasing the temperature. These results allowed us to verify a numerical model of complete operational cells (Barnes et al., Phys. Chem. Chem. Phys., DOI: 10.1039/c0cp01554g) and to relate the differences in j(rec) to physical processes in the devices. The difference between j(rec) in the light and dark can be explained by two factors: (1) an increase in the concentration of electron acceptor species (I(3)(-) and/or I(2)) when current is flowing under illumination relative to dark conditions where the current is flowing in the opposite direction, and (2) a non-trivial contribution from electron recombination to oxidised dye molecules under light conditions. More generally, the technique helps to assign the observed relationship between the components, processing and performance of DSSCs to more fundamental physical processes.

Modelling the physical multiphase interactions of HNO3 between snow and air on the Antarctic Plateau (Dome C) and coast (Halley)

NASA Astrophysics Data System (ADS)

Chan, Hoi Ga; Frey, Markus M.; King, Martin D.

2018-02-01

Emissions of nitrogen oxide (NOx = NO + NO2) from the photolysis of nitrate (NO3-) in snow affect the oxidising capacity of the lower troposphere especially in remote regions of high latitudes with little pollution. Current air-snow exchange models are limited by poor understanding of processes and often require unphysical tuning parameters. Here, two multiphase models were developed from physically based parameterisations to describe the interaction of nitrate between the surface layer of the snowpack and the overlying atmosphere. The first model is similar to previous approaches and assumes that below a threshold temperature, To, the air-snow grain interface is pure ice and above To a disordered interface (DI) emerges covering the entire grain surface. The second model assumes that air-ice interactions dominate over all temperatures below melting of ice and that any liquid present above the eutectic temperature is concentrated in micropockets. The models are used to predict the nitrate in surface snow constrained by year-round observations of mixing ratios of nitric acid in air at a cold site on the Antarctic Plateau (Dome C; 75°06' S, 123°33' E; 3233 m a.s.l.) and at a relatively warm site on the Antarctic coast (Halley; 75°35' S, 26°39' E; 35 m a.s.l). The first model agrees reasonably well with observations at Dome C (Cv(RMSE) = 1.34) but performs poorly at Halley (Cv(RMSE) = 89.28) while the second model reproduces with good agreement observations at both sites (Cv(RMSE) = 0.84 at both sites). It is therefore suggested that in winter air-snow interactions of nitrate are determined by non-equilibrium surface adsorption and co-condensation on ice coupled with solid-state diffusion inside the grain, similar to Bock et al. (2016). In summer, however, the air-snow exchange of nitrate is mainly driven by solvation into liquid micropockets following Henry's law with contributions to total surface snow NO3- concentrations of 75 and 80 % at Dome C and Halley, respectively. It is also found that the liquid volume of the snow grain and air-micropocket partitioning of HNO3 are sensitive to both the total solute concentration of mineral ions within the snow and pH of the snow. The second model provides an alternative method to predict nitrate concentration in the surface snow layer which is applicable over the entire range of environmental conditions typical for Antarctica and forms a basis for a future full 1-D snowpack model as well as parameterisations in regional or global atmospheric chemistry models.

Synthesis, characterization and DC conductivity studies of conducting polyaniline/PVA/Fly ash polymer composites

NASA Astrophysics Data System (ADS)

Revanasiddappa, M.; Swamy, D. Siddalinga; Vinay, K.; Ravikiran, Y. T.; Raghavendra, S. C.

2018-05-01

The present work is an investigation of dc conduction behaviour of conducting polyaniline/fly ash nano particles blended in polyvinyl Alcohol (PANI/PVA/FA) synthesized via in-situ polymerization technique using (NH4)2S2O8 as an oxidising agent with varying fly ash cenosphere by 10, 20, 30, 40 and 50 wt%. The structural characterization of the synthesised polymer composites was examined using FT-IR, XRD and SEM techniques. Dc conductivity as a function of temperature has been measured in the temperature range from 302K - 443K. The increase of conductivity with increasing temperature reveals semiconducting behaviour of the composites and shows an evidence for the transport properties of the composites.

Graphene nanoplate-MnO2 composites for supercapacitors: a controllable oxidation approach.

PubMed

Huang, Huajie; Wang, Xin

2011-08-01

Graphene nanoplate-MnO(2) composites have been synthesized by oxidising part of the carbon atoms in the framework of graphene nanoplates at ambient temperature. The composites were characterized by means of X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). It was found that the oxidation extent of the carbon atoms in the graphene framework in these composites was dependent on the reaction time, which also influenced their microstructure, morphology and electrochemical properties. Compared with MnO(2) nanolamellas, the nanocomposite prepared with a reaction time of 3 h reveals better electrochemical properties as a supercapacitor electrode material. This journal is © The Royal Society of Chemistry 2011

A direct and fast method to monitor lipid oxidation progress in model fatty acid methyl esters by high-performance size-exclusion chromatography.

PubMed

Márquez-Ruiz, G; Holgado, F; García-Martínez, M C; Dobarganes, M C

2007-09-21

A new method based on high-performance size-exclusion chromatography (HPSEC) is proposed to quantitate primary and secondary oxidation compounds in model fatty acid methyl esters (FAMEs). The method consists on simply injecting an aliquot sample in HPSEC, without preliminary isolation procedures neither addition of standard internal. Four groups of compounds can be quantified, namely, unoxidised FAME, oxidised FAME monomers including hydroperoxides, FAME dimers and FAME polymers. Results showed high repeatability and sensitivity, and substantial advantages versus determination of residual substrate by gas-liquid chromatography. Applicability of the method is shown through selected data obtained by numerous oxidation experiments on pure FAME, mainly methyl linoleate, at ambient and moderate temperatures.

Engineering cyanobacteria for direct biofuel production from CO2.

PubMed

Savakis, Philipp; Hellingwerf, Klaas J

2015-06-01

For a sustainable future of our society it is essential to close the global carbon cycle. Oxidised forms of carbon, in particular CO2, can be used to synthesise energy-rich organic molecules. Engineered cyanobacteria have attracted attention as catalysts for the direct conversion of CO2 into reduced fuel compounds. Proof of principle for this approach has been provided for a vast range of commodity chemicals, mostly energy carriers, such as short chain and medium chain alcohols. More recently, research has focused on the photosynthetic production of compounds with higher added value, most notably terpenoids. Below we review the recent developments that have improved the state-of-the-art of this approach and speculate on future developments. Copyright © 2014 Elsevier Ltd. All rights reserved.

Synthesis and Verification of Biobased Terephthalic Acid from Furfural

NASA Astrophysics Data System (ADS)

Tachibana, Yuya; Kimura, Saori; Kasuya, Ken-Ichi

2015-02-01

Exploiting biomass as an alternative to petrochemicals for the production of commodity plastics is vitally important if we are to become a more sustainable society. Here, we report a synthetic route for the production of terephthalic acid (TPA), the monomer of the widely used thermoplastic polymer poly(ethylene terephthalate) (PET), from the biomass-derived starting material furfural. Biobased furfural was oxidised and dehydrated to give maleic anhydride, which was further reacted with biobased furan to give its Diels-Alder (DA) adduct. The dehydration of the DA adduct gave phthalic anhydride, which was converted via phthalic acid and dipotassium phthalate to TPA. The biobased carbon content of the TPA was measured by accelerator mass spectroscopy and the TPA was found to be made of 100% biobased carbon.

The effects of oxaloacetate on hydrogen peroxide generation from ascorbate and epigallocatechin gallate in cell culture media: potential for altering cell metabolism.

PubMed

Long, Lee Hua; Halliwell, Barry

2012-01-06

Several phenolic compounds as well as ascorbate can oxidise in certain cell culture media (especially Dulbecco's modified Eagle's medium (DMEM)) to generate hydrogen peroxide. Addition of oxaloacetate decreased the levels of H(2)O(2) detected and the oxaloacetate was depleted. Oxaloacetate was approximately as effective as pyruvate in decreasing H(2)O(2) levels and more effective than α-ketoglutarate. Our data raise important issues to consider when interpreting the behaviour and metabolism of cells in culture (which are both altered by the oxidative stress of cell culture) and their apparent response to addition of autooxidisable compounds such as ascorbate and epigallocatechin gallate. Copyright © 2011 Elsevier Inc. All rights reserved.

Terminally Truncated Isopenicillin N Synthase Generates a Dithioester Product: Evidence for a Thioaldehyde Intermediate during Catalysis and a New Mode of Reaction for Non-Heme Iron Oxidases.

PubMed

McNeill, Luke A; Brown, Toby J N; Sami, Malkit; Clifton, Ian J; Burzlaff, Nicolai I; Claridge, Timothy D W; Adlington, Robert M; Baldwin, Jack E; Rutledge, Peter J; Schofield, Christopher J

2017-09-18

Isopenicillin N synthase (IPNS) catalyses the four-electron oxidation of a tripeptide, l-δ-(α-aminoadipoyl)-l-cysteinyl-d-valine (ACV), to give isopenicillin N (IPN), the first-formed β-lactam in penicillin and cephalosporin biosynthesis. IPNS catalysis is dependent upon an iron(II) cofactor and oxygen as a co-substrate. In the absence of substrate, the carbonyl oxygen of the side-chain amide of the penultimate residue, Gln330, co-ordinates to the active-site metal iron. Substrate binding ablates the interaction between Gln330 and the metal, triggering rearrangement of seven C-terminal residues, which move to take up a conformation that extends the final α-helix and encloses ACV in the active site. Mutagenesis studies are reported, which probe the role of the C-terminal and other aspects of the substrate binding pocket in IPNS. The hydrophobic nature of amino acid side-chains around the ACV binding pocket is important in catalysis. Deletion of seven C-terminal residues exposes the active site and leads to formation of a new type of thiol oxidation product. The isolated product is shown by LC-MS and NMR analyses to be the ene-thiol tautomer of a dithioester, made up from two molecules of ACV linked between the thiol sulfur of one tripeptide and the oxidised cysteinyl β-carbon of the other. A mechanism for its formation is proposed, supported by an X-ray crystal structure, which shows the substrate ACV bound at the active site, its cysteinyl β-carbon exposed to attack by a second molecule of substrate, adjacent. Formation of this product constitutes a new mode of reaction for IPNS and non-heme iron oxidases in general. © 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

Speleothem records of acid sulphate deposition and organic carbon mobilisation

NASA Astrophysics Data System (ADS)

Wynn, Peter; Fairchild, Ian; Bourdin, Clement; Baldini, James; Muller, Wolfgang; Hartland, Adam; Bartlett, Rebecca

2017-04-01

Dramatic increases in measured surface water DOC in recent decades have been variously attributed to either temperature rise, or destabilisation of long-term soil carbon pools following sulphur peak emissions status. However, whilst both drivers of DOC dynamics are plausible, they remain difficult to test due to the restricted nature of the available records of riverine DOC flux (1978 to present), and the limited availability of SO2 emissions inventory data at the regional scale. Speleothems offer long term records of both sulphur and carbon. New techniques to extract sulphur concentrations and isotopes from speleothem calcite have enabled archives of pollution history and environmental acidification to be reconstructed. Due to the large dynamic range in sulphur isotopic values from end member sources (marine aerosol +21 ‰ to continental biogenic emissions -30 ‰) and limited environmental fractionation under oxidising conditions, sulphur isotopes form an ideal tracer of industrial pollution and environmental acidification in the palaeo-record. We couple this acidification history to the carbon record, using organic matter fluorescence and trace metals. Trace metal ratios and abundance can be used to infer the type and size of organic ligand and are therefore sensitive to changes in temperature as a driver of organic carbon processing and biodegradation. This allows fluorescent properties and ratios of trace metals in speleothem carbonate to be used to represent both the flux of organic carbon into the cave as well as the degradation pathway. Here we present some of the first results of this work, exploring sulphur acidification as a mechanistic control on carbon solubility and export throughout the twentieth century.

The Burn Rate of Calcium Sulfate Dihydrate-Aluminum Thermites.

PubMed

Govender, Desania Raquel; Focke, Walter Wilhelm; Tichapondwa, Shepherd Masimba; Cloete, William Edward

2018-05-29

The energetics of cast calcium sulfate dihydrate-aluminium thermites was investigated. The casts were prepared form water slurries with a solids content of xxx wt-%. The base case thermite comprised 60 wt-% calcium sulfate dihydrate as the oxidiser with 40 wt-% aluminium as fuel. The heat of hydration of the base case was 59 ± 8 kJkg-1 and the setting time was zzz min. The compressive strength reached 2.9 ± 0.2 MPa after three days drying in ambient air. The open air burn rate was 12.0 ± 1.6 mm s-1 and a maximum surface temperature of 1370 ± 64 °C was recorded with a pyrometer. Bomb calorimetry indicated an energy output of 8.0 ± 1.1 MJ kg-1, slightly lower than predicted by the EKVI thermodynamic simulation. Substitution of 10 wt-% of the oxidant with copper sulfate pentahydrate significantly decreased the setting time of the casts to about yyy min. The density of the castings was varied by either adding hollow sodium borosilicate glass spheres or by adding excess water during the casting process. The addition of the hollow glass spheres caused a decrease in the burning rate. The burning rate of the base case was not affected materially by the addition of excess water. However, it did increase the burning rate of the copper sulfate pentahydrate-modified thermite. Dehydration of the casts by thermal treatments at either 155 °C or 200 °C also led to significant increases in the burning rate.

Assessment of farm soil, biochar, compost and weathered pine mulch to mitigate methane emissions.

PubMed

Syed, Rashad; Saggar, Surinder; Tate, Kevin; Rehm, Bernd H A

2016-11-01

Previous studies have demonstrated the effective utility of volcanic pumice soil to mitigate both high and low levels of methane (CH 4 ) emissions through the activity of both γ-proteobacterial (type I) and α-proteobacterial (type II) aerobic methanotrophs. However, the limited availability of volcanic pumice soil necessitates the assessment of other farm soils and potentially suitable, economical and widely available biofilter materials. The potential biofilter materials, viz. farm soil (isolated from a dairy farm effluent pond bank area), pine biochar, garden waste compost and weathered pine bark mulch, were inoculated with a small amount of volcanic pumice soil. Simultaneously, a similar set-up of potential biofilter materials without inoculum was studied to understand the effect of the inoculum on the ability of these materials to oxidise CH 4 and their effect on methanotroph growth and activity. These materials were incubated at 25 °C with periodic feeding of CH 4 , and flasks were aerated with air (O 2 ) to support methanotroph growth and activity by maintaining aerobic conditions. The efficiency of CH 4 removal was monitored over 6 months. All materials supported the growth and activity of methanotrophs. However, the efficiency of CH 4 removal by all the materials tested fluctuated between no or low removal (0-40 %) and high removal phases (>90 %), indicating biological disturbances rather than physico-chemical changes. Among all the treatments, CH 4 removal was consistently high (>80 %) in the inoculated farm soil and inoculated biochar, and these were more resilient to changes in the methanotroph community. The CH 4 removal from inoculated farm soil and inoculated biochar was further enhanced (up to 99 %) by the addition of a nutrient solution. Our results showed that (i) farm soil and biochar can be used as a biofilter material by inoculating with an active methanotroph community, (ii) an abundant population of α-proteobacterial methanotrophs is essential for effective and stable CH 4 removal and (iii) addition of nutrients enhances the growth and activity of methanotrophs in the biofilter materials. Further studies are underway to assess the feasibility of these materials at small plot and field scales.

The role of tannins in conventional and membrane treatment of tannery wastewater.

PubMed

Munz, G; De Angelis, D; Gori, R; Mori, G; Casarci, M; Lubello, C

2009-05-30

The role that tannins play in tannery wastewater treatment has been evaluated employing a pilot Membrane Bioreactor (MBR) plant and a full scale Conventional Activated Sludge Process (CASP) plant conducted in parallel. The proposed methodology has established the preliminary use of respirometry to examine the biodegradability of a selection of commercial products (synthetic and natural tannins); the subsequent analysis, by means of spectrophotometric reading and RP-IPC (Reverse-Phase Ion-Pair) liquid chromatography, estimates the concentrations of natural tannins and naphthalenesulfonic tanning agents in the influent and effluent samples. The results show that a consistent percentage of the Total Organic Carbon (TOC) in the effluent of the biological phase of the plants is attributable to the presence of natural and synthetic (Sulfonated Naphthalene-Formaldehyde Condensates, SNFC) tannins (17% and 14% respectively). The titrimetric tests that were aimed at evaluating the levels of inhibition on the nitrifying biomass samples did not allow a direct inhibiting effect to be associated with the concentration levels of the tannin in the effluent. Nonetheless, the reduced specific growth rates of ammonium and nitrite oxidising bacteria imply that a strong environmental pressure is present, if not necessarily due to the concentration of tannins, due to the wastewater as a whole. The differences that have emerged by comparing the two technologies (CASP and MBR), in regards to the role that tannins play in terms of biodegradability, did not appear to be significant.

How might you compare mitochondria from different tissues and different species?

PubMed

Hulbert, A J; Turner, Nigel; Hinde, Jack; Else, Paul; Guderley, Helga

2006-02-01

Mitochondria were isolated from the liver, kidney and mixed hindlimb skeletal muscle of three vertebrate species; the laboratory rat Rattus norvegicus, the bearded dragon lizard Pogona vitticeps, and the cane toad Bufo marinus. These vertebrate species are approximately the same body mass and have similar body temperatures. The content of cytochromes B, C, C1, and A were measured in these isolated mitochondria by oxidised-reduced difference spectra. Adenine nucleotide translocase (ANT) was measured by titration of mitochondrial respiration with carboxyactractyloside and the protein and phospholipid content of isolated mitochondria were also measured. Fatty acid composition of mitochondrial phospholipids was measured. Mitochondrial respiration was measured at 37 degrees C under states III and IV conditions as well as during oligomycin inhibition. Species differed in the ratios of different mitochondrial cytochromes. Muscle mitochondria differed from kidney and liver mitochondria by having a higher ANT content relative to cytochrome content. Respiration rates were compared relative to a number of denominators and found to be most variable when expressed relative to mitochondrial protein content and least variable when expressed relative to mitochondrial cytochrome A and ANT content. The turnover of cytochromes was calculated and found to vary between 1 and 94 electrons s(-1). The molecular activity of mitochondrial cytochromes was found to be significantly positively correlated with the relative polyunsaturation of mitochondrial membrane lipids.

Caloric restriction or telmisartan control dyslipidemia and nephropathy in obese diabetic Zücker rats

PubMed Central

2014-01-01

Background The obese Zücker diabetic fatty male rat (ZDF:Gmi™-fa) is an animal model of type II diabetes associated with obesity and related metabolic disturbances like dyslipidaemia and diabetic nephropathy. In addition, diabetic dyslipidaemia has been linked to vascular and glomerular damage too. Dietary fat restriction is a current strategy to tackle obesity and, telmisartan, as a renoprotective agent, may mediate cholesterol efflux by activating PPARγ. To test the hypothesis that both therapeutical alternatives may influence dyslipidaemia and nephropathy in the ZDF rat, we studied their effect on development of diabetes. Methods Male Zücker Diabetic Fatty (ZDF) rats received a low-calorie diet, vehicle or telmisartan for 9 weeks. Blood samples were obtained for analyses of lipids and lipoproteins, LDL-oxidisability, HDL structural and functional properties. Urinalysis was carried out to estimate albumin loss. At the end of the experimental period, rats were sacrificed, liver extracted and APOA1 mRNA quantified. Results Results indicated that low-calorie diet and telmisartan can slower the onset of overt hyperglycaemia and renal damage assessed as albuminuria. Both interventions decreased the oxidative susceptibility of LDL and hepatic APOA1 mRNA expression but only dietary restriction lowered hyperlipidaemia. Conclusion Either a dietary or pharmacologic interventions with telmisartan have important beneficial effects in terms of LDL oxidative susceptibility and progression of albuminuria in obesity related type II diabetes. PMID:24468233

Quantitative methylene blue decolourisation assays as rapid screening tools for assessing the efficiency of catalytic reactions.

PubMed

Kruid, Jan; Fogel, Ronen; Limson, Janice Leigh

2017-05-01

Identifying the most efficient oxidation process to achieve maximum removal of a target pollutant compound forms the subject of much research. There exists a need to develop rapid screening tools to support research in this area. In this work we report on the development of a quantitative assay as a means for identifying catalysts capable of decolourising methylene blue through the generation of oxidising species from hydrogen peroxide. Here, a previously described methylene blue test strip method was repurposed as a quantitative, aqueous-based spectrophotometric assay. From amongst a selection of metal salts and metallophthalocyanine complexes, monitoring of the decolourisation of the cationic dye methylene blue (via Fenton-like and non-Fenton oxidation reactions) by the assay identified the following to be suitable oxidation catalysts: CuSO 4 (a Fenton-like catalyst), iron(II)phthalocyanine (a non-Fenton oxidation catalyst), as well as manganese(II) phthalocyanine. The applicability of the method was examined for the removal of bisphenol A (BPA), as measured by HPLC, during parallel oxidation experiments. The order of catalytic activity was identified as FePc > MnPc > CuSO 4 for both BPA and MB. The quantitative MB decolourisation assay may offer a rapid method for screening a wide range of potential catalysts for oxidation processes. Copyright © 2017 Elsevier Ltd. All rights reserved.

Moderate Champagne consumption promotes an acute improvement in acute endothelial-independent vascular function in healthy human volunteers.

PubMed

Vauzour, David; Houseman, Emily J; George, Trevor W; Corona, Giulia; Garnotel, Roselyne; Jackson, Kim G; Sellier, Christelle; Gillery, Philippe; Kennedy, Orla B; Lovegrove, Julie A; Spencer, Jeremy P E

2010-04-01

Epidemiological studies have suggested an inverse correlation between red wine consumption and the incidence of CVD. However, Champagne wine has not been fully investigated for its cardioprotective potential. In order to assess whether acute and moderate Champagne wine consumption is capable of modulating vascular function, we performed a randomised, placebo-controlled, cross-over intervention trial. We show that consumption of Champagne wine, but not a control matched for alcohol, carbohydrate and fruit-derived acid content, induced an acute change in endothelium-independent vasodilatation at 4 and 8 h post-consumption. Although both Champagne wine and the control also induced an increase in endothelium-dependent vascular reactivity at 4 h, there was no significant difference between the vascular effects induced by Champagne or the control at any time point. These effects were accompanied by an acute decrease in the concentration of matrix metalloproteinase (MMP-9), a significant decrease in plasma levels of oxidising species and an increase in urinary excretion of a number of phenolic metabolites. In particular, the mean total excretion of hippuric acid, protocatechuic acid and isoferulic acid were all significantly greater following the Champagne wine intervention compared with the control intervention. Our data suggest that a daily moderate consumption of Champagne wine may improve vascular performance via the delivery of phenolic constituents capable of improving NO bioavailability and reducing matrix metalloproteinase activity.

Oxidative stress induced by potassium bromate exposure results in altered tight junction protein expression in renal proximal tubule cells.

PubMed

Limonciel, Alice; Wilmes, Anja; Aschauer, Lydia; Radford, Robert; Bloch, Katarzyna M; McMorrow, Tara; Pfaller, Walter; van Delft, Joost H; Slattery, Craig; Ryan, Michael P; Lock, Edward A; Jennings, Paul

2012-11-01

Potassium bromate (KBrO(3)) is an oxidising agent that has been widely used in the food and cosmetic industries. It has shown to be both a nephrotoxin and a renal carcinogen in in vivo and in vitro models. Here, we investigated the effects of KBrO(3) in the human and rat proximal tubular cell lines RPTEC/TERT1 and NRK-52E. A genome-wide transcriptomic screen was carried out from cells exposed to a sub-lethal concentration of KBrO(3) for 6, 24 and 72 h. Pathway analysis identified "glutathione metabolism", "Nrf2-mediated oxidative stress" and "tight junction (TJ) signalling" as the most enriched pathways. TJ signalling was less impacted in the rat model, and further studies revealed low transepithelial electrical resistance (TEER) and an absence of several TJ proteins in NRK-52E cells. In RPTEC/TERT1 cells, KBrO(3) exposure caused a decrease in TEER and resulted in altered expression of several TJ proteins. N-Acetylcysteine co-incubation prevented these effects. These results demonstrate that oxidative stress has, in conjunction with the activation of the cytoprotective Nrf2 pathway, a dramatic effect on the expression of tight junction proteins. The further understanding of the cross-talk between these two pathways could have major implications for epithelial repair, carcinogenesis and metastasis.

Oxidative stress markers during a course of hyperthyroidism.

PubMed

Lampka, Magdalena; Junik, Roman; Nowicka, Anna; Kopczyńska, Ewa; Tyrakowski, Tomasz; Odrowaz-Sypniewska, Grazyna

2006-01-01

Previous studies have shown the presence of oxidative stress in hyperthyroid patients. The aim of this study was to evaluate the influence of hyperthyroidism on lipid peroxidation, plasma lipoprotein oxidation and antioxidant status. We have estimated the clinical utility of the biochemical parameters analysed as markers of oxidative stress in hyperthyroidism. Twenty five patients with overt hyperthyroidism because of Graves' disease or toxic multinodular goitre and 20 healthy subjects were included in the study. Lipid peroxidation was evaluated by measurement of peroxides and malondialdehyde with 4-hydroxynonenal (MDA + 4-HNE) concentrations. Autoantibodies against oxidised LDL (anti-oxLDL) were assayed as a marker of lipoprotein oxidation. Changes in the antioxidant defence system were estimated by measurement of total antioxidant status in serum (TAS) and erythrocyte superoxide dismutase activity (SOD). A significant increase in serum concentration of peroxides and MDA + 4-HNE was observed in patients with hyperthyroidism. However, no difference was found in anti-oxLDL concentration and antioxidant status parameters (TAS, SOD) between the control group and the patient group. Our results indicate an intensification of the oxidative processes caused by an excess of thyroid hormones, which is not accompanied by a response from the antioxidant system. Elevated concentrations of lipid peroxidation products in serum, both peroxides and malondialdehyde with 4-hydroxynonenal, may be useful as markers of oxidative stress during the course of hyperthyroidism.

Electrochemistry of uranium in molten LiF-CaF2

NASA Astrophysics Data System (ADS)

Nourry, C.; Souček, P.; Massot, L.; Malmbeck, R.; Chamelot, P.; Glatz, J.-P.

2012-11-01

This article is focused on the electrochemical behaviour of U ions in molten LiF-CaF2 (79-21 wt.%) eutectic. On a W electrode, U(III) is reduced in one step to U metal and U(III) can be also oxidised to U(IV). Both systems were studied by cyclic and square wave voltammetry. Reversibility of both systems for both techniques was verified and number of exchanged electrons was determined, as well as diffusion coefficients for U(III) and U(IV). The results are in a good agreement with previous studies. On a Ni electrode, the depolarisation effect due to intermetallic compounds formation was observed. Electrorefining of U metal in a melt containing U and Gd ions was carried out using a reactive Ni electrode with promising results.

Synthesis and Verification of Biobased Terephthalic Acid from Furfural

PubMed Central

Tachibana, Yuya; Kimura, Saori; Kasuya, Ken-ichi

2015-01-01

Exploiting biomass as an alternative to petrochemicals for the production of commodity plastics is vitally important if we are to become a more sustainable society. Here, we report a synthetic route for the production of terephthalic acid (TPA), the monomer of the widely used thermoplastic polymer poly(ethylene terephthalate) (PET), from the biomass-derived starting material furfural. Biobased furfural was oxidised and dehydrated to give maleic anhydride, which was further reacted with biobased furan to give its Diels-Alder (DA) adduct. The dehydration of the DA adduct gave phthalic anhydride, which was converted via phthalic acid and dipotassium phthalate to TPA. The biobased carbon content of the TPA was measured by accelerator mass spectroscopy and the TPA was found to be made of 100% biobased carbon. PMID:25648201

Ammonia oxidation: Ecology, physiology, biochemistry and why they must all come together.

PubMed

Lehtovirta-Morley, Laura E

2018-05-01

Ammonia oxidation is a fundamental core process in the global biogeochemical nitrogen cycle. Oxidation of ammonia (NH3) to nitrite (NO2 -) is the first and rate-limiting step in nitrification and is carried out by distinct groups of microorganisms. Ammonia oxidation is essential for nutrient turnover in most terrestrial, aquatic and engineered ecosystems and plays a major role, both directly and indirectly, in greenhouse gas production and environmental damage. Although ammonia oxidation has been studied for over a century, this research field has been galvanised in the past decade by the surprising discoveries of novel ammonia oxidising microorganisms. This review reflects on the ammonia oxidation research to date and discusses the major gaps remaining in our knowledge of the biology of ammonia oxidation.

Mineral-microbial interaction in long term experiments with sandstones and reservoir fluids exposed to CO2

NASA Astrophysics Data System (ADS)

Kasina, Monika; Morozova, Daria; Pellizzari, Linda; Würdemann, Hilke

2013-04-01

Microorganisms represent very effective geochemical catalysts, and may influence the process of the CO2 storage significantly. The goal of this study is to characterize the interactions between minerals and microorganisms during their exposure to the CO2 in a long term experiment in high pressure vessels to better understand the influence of biological processes on the composition of the reservoir sandstones and the long term stability of CO2 storage. The natural gas reservoir, proposed for the CO2 storage is characterized by high salinity (up to 420 g/l) and temperatures around 130°C, at depth of approximately 3.5 km. Microbial community of the reservoir fluid samples was dominated by different H2-oxidising, thiosulfate-oxidising and biocorrosive thermophilic bacteria as well as microorganisms similar to representatives from other deep environments, which have not previously been cultivated. The cells were attached to particles and were difficult to detect because of low cell numbers (Morozova et al., 2011). For the long term experiments, the autoclaved rock core samples from the core deposit were grinded, milled to the size of 0.5 mm and incubated with fresh reservoir fluids as inoculum for indigenous microorganisms in a N2/CH4/H2-atmosphere in high pressure vessels at a temperature of 80°C and pressure of 40 bars. Incubation was performed under lower temperature than in situ in order to favor the growth of the dormant microorganisms. After three months of incubation samples were exposed to high CO2 concentrations by insufflating it into the vessels. The sampling of rock and fluid material was executed 10 and 21 months after start of the experiment. Mineralogical analyses performed using XRD and SEM - EDS showed that main mineral components are quartz, feldspars, dolomite, anhydrite and calcite. Chemical fluid analyses using ICP-MS and ICP-OES showed that after CO2 exposure increasing Si4+ content in the fluid was noted after first sampling (ca. 25 relative %), whereas after the second sampling it decreased (to 31 relative %) in comparison to the reservoir fluid sample. This may suggest dissolution of silicate minerals at first, and secondary precipitation at second stage of experiment. In addition, immobilization of heavy metals dispersed within silicate minerals was also detected. An increase of Ca (3.2 up to 13% relative), SO4 (up to 14 relative %) and Fetot (47 and 24% relative) were also detected after first and second sampling respectively and may suggest dissolution of cements and iron rich minerals. The concentration of organic acids increased relatively by 12.5 % and 25% after first and second sampling respectively might be an indication for metabolic activity of microorganism or an effect of mobilisation due to CO2 exposure. The presence of newly formed mineral phases was detected using SEM-EDS. Quartz, albite and illite precipitation is a common process in all studied samples. However only illite is considered to be of bacterial origin, nevertheless its crystallization can also occur as a consequence of inorganic diagenetic processes. Further analyses of the microbial community composition, quantity and activity will bring a more insight into the CO2 exposure processes. Daria Morozova, Dagmar Kock, Martin Krüger, and Hilke Würdemann. Biogeochemical and microbial characterization of reservoir fluids from a gas field (Altmark). Geotechnologien 2011

Biological definition of multiple chemical sensitivity from redox state and cytokine profiling and not from polymorphisms of xenobiotic-metabolizing enzymes

DOE Office of Scientific and Technical Information (OSTI.GOV)

De Luca, Chiara; Scordo, Maria G.; Cesareo, Eleonora

Background: Multiple chemical sensitivity (MCS) is a poorly clinically and biologically defined environment-associated syndrome. Although dysfunctions of phase I/phase II metabolizing enzymes and redox imbalance have been hypothesized, corresponding genetic and metabolic parameters in MCS have not been systematically examined. Objectives: We sought for genetic, immunological, and metabolic markers in MCS. Methods: We genotyped patients with diagnosis of MCS, suspected MCS and Italian healthy controls for allelic variants of cytochrome P450 isoforms (CYP2C9, CYP2C19, CYP2D6, and CYP3A5), UDP-glucuronosyl transferase (UGT1A1), and glutathione S-transferases (GSTP1, GSTM1, and GSTT1). Erythrocyte membrane fatty acids, antioxidant (catalase, superoxide dismutase (SOD)) and glutathione metabolizing (GST,more » glutathione peroxidase (Gpx)) enzymes, whole blood chemiluminescence, total antioxidant capacity, levels of nitrites/nitrates, glutathione, HNE-protein adducts, and a wide spectrum of cytokines in the plasma were determined. Results: Allele and genotype frequencies of CYPs, UGT, GSTM, GSTT, and GSTP were similar in the Italian MCS patients and in the control populations. The activities of erythrocyte catalase and GST were lower, whereas Gpx was higher than normal. Both reduced and oxidised glutathione were decreased, whereas nitrites/nitrates were increased in the MCS groups. The MCS fatty acid profile was shifted to saturated compartment and IFNgamma, IL-8, IL-10, MCP-1, PDGFbb, and VEGF were increased. Conclusions: Altered redox and cytokine patterns suggest inhibition of expression/activity of metabolizing and antioxidant enzymes in MCS. Metabolic parameters indicating accelerated lipid oxidation, increased nitric oxide production and glutathione depletion in combination with increased plasma inflammatory cytokines should be considered in biological definition and diagnosis of MCS.« less

Ketamine induction of p53-dependent apoptosis and oxidative stress in zebrafish (Danio rerio) embryos.

PubMed

Félix, Luís M; Vidal, Ana M; Serafim, Cindy; Valentim, Ana M; Antunes, Luís M; Monteiro, Sandra M; Matos, Manuela; Coimbra, Ana M

2018-06-01

Ketamine is a widely used pharmaceutical that has been detected in water sources worldwide. Zebrafish embryos were used in this study to investigate the oxidative stress and apoptotic signals following a 24h exposure to different ketamine concentrations (0, 50, 70 and 90 mg L -1 ). Early blastula embryos (∼2 h post fertilisation-hpf) were exposed for 24 h and analysed at 8 and 26 hpf. Reactive oxygen species and apoptotic cells were identified in vivo, at 26 hpf. Enzymatic activities (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), lactate dehydrogenase (LDH) and acetylcholinesterase (AChE)), glutathione levels (oxidised (GSSG) and reduced (GSH)), oxidative damage (lipid peroxidation (LPO) and protein carbonyls (CO)) as well as oxidative stress (gclc, gstp1, sod1 and cat), apoptosis (casp3a, casp6, casp8, casp9, aifm1 and tp53) and cell proliferation (pcna) related-genes were evaluated at 8 and 26 hpf. Caspase (3 and 9) activity was also determined at both time-points by colorimetric methods. Superoxide dismutase (SOD), catalase (CAT), glutathione levels (GSSG), caspase-9 and reactive oxygen species (ROS) were shown to be affected by ketamine exposure while in vivo analysis showed no difference in ROS. A significant up-regulation of superoxide dismutase (sod1) and catalase (cat) genes expression was also perceived. Ketamine-induced apoptosis was observed in vivo and confirmed by the apoptotic-related genes up-regulation. The overall results suggest that ketamine induced oxidative stress and apoptosis through the involvement of p53-dependent pathways in zebrafish embryos which could be important for the evaluation of the overall risk of ketamine in aquatic environments. Copyright © 2018 Elsevier Ltd. All rights reserved.

Gaseous nitrogen losses from a forest site in the North Tyrolean Limestone Alps.

PubMed

Härtel, Elisabeth; Zechmeister-Boltenstern, Sophie; Gerzabck, Martin

2002-01-01

Microorganisms are responsible for the mineralisation of organic nitrogen in soils. NH4+ can be further oxidised to NO3- during nitrification and NO3- can be reduced to gaseous nitrogen compounds during denitrification. During both processes, nitrous oxide (N2O), which is known as greenhouse gas, can be lost from the ecosystem. The aim of this study was to quantify N2O emissions and the internal microbial N cycle including net N mineralisation and net nitrification in a montane forest ecosystem in the North Tyrolean Limestone Alps during an 18-month measurement period and to estimate the importance of these fluxes in comparison with other components of the N cycle. Gas samples were taken every 2 weeks using the closed chamber method. Additionally, CO2 emission rates were measured to estimate soil respiration activity. Net mineralisation and net nitrification rates were determined by the buried bag method every month. Ion exchange resin bags were used to determine the N availability in the root zone. Mean N2O emission rate was 0.9 kg N ha(-1) a(-1), which corresponds to 5% of the N deposited in the forest ecosystem. The main influencing factors were air and soil temperature and NO3- accumulated on the ion exchange resin bags. In the course of net ammonification, 14 kg NH4+-N ha(-1) were produced per year. About the same amount of NO3--N was formed during nitrification, indicating a rather complete nitrification going on at the site. NO3- concentrations found on the ion exchange resin bags were about 3 times as high as NO3- produced during net nitrification, indicating substantial NO3- immobilisation. The results of this study indicate significant nitrification activities taking place at the Mühleggerköpfl.

Basic regulatory principles of Escherichia coli's electron transport chain for varying oxygen conditions.

PubMed

Henkel, Sebastian G; Ter Beek, Alexander; Steinsiek, Sonja; Stagge, Stefan; Bettenbrock, Katja; de Mattos, M Joost Teixeira; Sauter, Thomas; Sawodny, Oliver; Ederer, Michael

2014-01-01

For adaptation between anaerobic, micro-aerobic and aerobic conditions Escherichia coli's metabolism and in particular its electron transport chain (ETC) is highly regulated. Although it is known that the global transcriptional regulators FNR and ArcA are involved in oxygen response it is unclear how they interplay in the regulation of ETC enzymes under micro-aerobic chemostat conditions. Also, there are diverse results which and how quinones (oxidised/reduced, ubiquinone/other quinones) are controlling the ArcBA two-component system. In the following a mathematical model of the E. coli ETC linked to basic modules for substrate uptake, fermentation product excretion and biomass formation is introduced. The kinetic modelling focusses on regulatory principles of the ETC for varying oxygen conditions in glucose-limited continuous cultures. The model is based on the balance of electron donation (glucose) and acceptance (oxygen or other acceptors). Also, it is able to account for different chemostat conditions due to changed substrate concentrations and dilution rates. The parameter identification process is divided into an estimation and a validation step based on previously published and new experimental data. The model shows that experimentally observed, qualitatively different behaviour of the ubiquinone redox state and the ArcA activity profile in the micro-aerobic range for different experimental conditions can emerge from a single network structure. The network structure features a strong feed-forward effect from the FNR regulatory system to the ArcBA regulatory system via a common control of the dehydrogenases of the ETC. The model supports the hypothesis that ubiquinone but not ubiquinol plays a key role in determining the activity of ArcBA in a glucose-limited chemostat at micro-aerobic conditions.

Modelling of the dissolution and reprecipitation of uranium under oxidising conditions in the zone of shallow groundwater circulation.

PubMed

Dutova, Ekaterina M; Nikitenkov, Aleksei N; Pokrovskiy, Vitaly D; Banks, David; Frengstad, Bjørn S; Parnachev, Valerii P

2017-11-01

Generic hydrochemical modelling of a grantoid-groundwater system, using the Russian software "HydroGeo", has been carried out with an emphasis on simulating the accumulation of uranium in the aqueous phase. The baseline model run simulates shallow granitoid aquifers (U content 5 ppm) under conditions broadly representative of southern Norway and southwestern Siberia: i.e. temperature 10 °C, equilibrated with a soil gas partial CO 2 pressure (P CO2 , open system) of 10 -2.5 atm. and a mildly oxidising redox environment (Eh = +50 mV). Modelling indicates that aqueous uranium accumulates in parallel with total dissolved solids (or groundwater mineralisation M - regarded as an indicator of degree of hydrochemical evolution), accumulating most rapidly when M = 550-1000 mg L -1 . Accumulation slows at the onset of saturation and precipitation of secondary uranium minerals at M = c. 1000 mg L -1 (which, under baseline modelling conditions, also corresponds approximately to calcite saturation and transition to Na-HCO 3 hydrofacies). The secondary minerals are typically "black" uranium oxides of mixed oxidation state (e.g. U 3 O 7 and U 4 O 9 ). For rock U content of 5-50 ppm, it is possible to generate a wide variety of aqueous uranium concentrations, up to a maximum of just over 1 mg L -1 , but with typical concentrations of up to 10 μg L -1 for modest degrees of hydrochemical maturity (as indicated by M). These observations correspond extremely well with real groundwater analyses from the Altai-Sayan region of Russia and Norwegian crystalline bedrock aquifers. The timing (with respect to M) and degree of aqueous uranium accumulation are also sensitive to Eh (greater mobilisation at higher Eh), uranium content of rocks (aqueous concentration increases as rock content increases) and P CO2 (low P CO2 favours higher pH, rapid accumulation of aqueous U and earlier saturation with respect to uranium minerals). Copyright © 2017 Elsevier Ltd. All rights reserved.

Facultative methanotrophs are abundant at terrestrial natural gas seeps.

PubMed

Farhan Ul Haque, Muhammad; Crombie, Andrew T; Ensminger, Scott A; Baciu, Calin; Murrell, J Colin

2018-06-28

Natural gas contains methane and the gaseous alkanes ethane, propane and butane, which collectively influence atmospheric chemistry and cause global warming. Methane-oxidising bacteria, methanotrophs, are crucial in mitigating emissions of methane as they oxidise most of the methane produced in soils and the subsurface before it reaches the atmosphere. Methanotrophs are usually obligate, i.e. grow only on methane and not on longer chain alkanes. Bacteria that grow on the other gaseous alkanes in natural gas such as propane have also been characterised, but they do not grow on methane. Recently, it was shown that the facultative methanotroph Methylocella silvestris grew on ethane and propane, other components of natural gas, in addition to methane. Therefore, we hypothesised that Methylocella may be prevalent at natural gas seeps and might play a major role in consuming all components of this potent greenhouse gas mixture before it is released to the atmosphere. Environments known to be exposed to biogenic methane emissions or thermogenic natural gas seeps were surveyed for methanotrophs. 16S rRNA gene amplicon sequencing revealed that Methylocella were the most abundant methanotrophs in natural gas seep environments. New Methylocella-specific molecular tools targeting mmoX (encoding the soluble methane monooxygenase) by PCR and Illumina amplicon sequencing were designed and used to investigate various sites. Functional gene-based assays confirmed that Methylocella were present in all of the natural gas seep sites tested here. This might be due to its ability to use methane and other short chain alkane components of natural gas. We also observed the abundance of Methylocella in other environments exposed to biogenic methane, suggesting that Methylocella has been overlooked in the past as previous ecological studies of methanotrophs often used pmoA (encoding the alpha subunit of particulate methane monooxygenase) as a marker gene. New biomolecular tools designed in this study have expanded our ability to detect, and our knowledge of the environmental distribution of Methylocella, a unique facultative methanotroph. This study has revealed that Methylocella are particularly abundant at natural gas seeps and may play a significant role in biogeochemical cycling of gaseous hydrocarbons.

Shelf-life of minimally processed cabbage treated with neutral electrolysed oxidising water and stored under equilibrium modified atmosphere.

PubMed

Gómez-López, Vicente M; Ragaert, Peter; Ryckeboer, Jaak; Jeyachchandran, Visvalingam; Debevere, Johan; Devlieghere, Frank

2007-06-10

Minimally processed vegetables (MPV) have a short shelf-life. Neutral electrolysed oxidising water (NEW) is a novel decontamination method. The objective of this study was to test the potential of NEW to extend the shelf-life of a MPV, namely shredded cabbage. Samples of shredded cabbage were immersed in NEW containing 40 mg/L of free chlorine or tap water (control) up to 5 min, and then stored under equilibrium modified atmosphere at 4 degrees C and 7 degrees C. Proliferation of aerobic mesophilic bacteria, psychrotrophic bacteria, lactic acid bacteria and yeasts were studied during the shelf-life. Also pH and sensorial quality of the samples as well as O(2) and CO(2) composition of the headspace of the bags was evaluated. From the microbial groups, only psychrotrophic counts decreased significantly (P<0.05) due to the effect of NEW, but the counts in treated samples and controls were similar after 3 days of storage at 4 degrees C and 7 degrees C. Packaging configurations kept O(2) concentration around 5% and prevented CO(2) accumulation. pH increased from 6.1-6.2 to 6.4 during the shelf-life. No microbial parameter reached unacceptable counts after 14 days at 4 degrees C and 8 days of storage at 7 degrees C. The shelf-life of controls stored at 4 degrees C was limited to 9 days by overall visual quality (OVQ), while samples treated with NEW remained acceptable during the 14 days of the experiment. The shelf-life of controls stored at 7 degrees C was limited to 6 days by OVQ and browning, while that of samples treated with NEW were limited to 9 days by OVQ, browning and dryness. According to these results, a shelf-life extension of at least 5 days and 3 days in samples stored respectively at 4 degrees C and 7 degrees C can be achieved by treating shredded cabbage with NEW. NEW seems to be a promising method to prolong the shelf-life of MPV.

The role of highly oxygenated molecules (HOMs) in determining the composition of ambient ions in the boreal forest

NASA Astrophysics Data System (ADS)

Bianchi, Federico; Garmash, Olga; He, Xucheng; Yan, Chao; Iyer, Siddharth; Rosendahl, Ida; Xu, Zhengning; Rissanen, Matti P.; Riva, Matthieu; Taipale, Risto; Sarnela, Nina; Petäjä, Tuukka; Worsnop, Douglas R.; Kulmala, Markku; Ehn, Mikael; Junninen, Heikki

2017-11-01

In order to investigate the negative ions in the boreal forest we have performed measurements to chemically characterise the composition of negatively charged clusters containing highly oxygenated molecules (HOMs). Additionally, we compared this information with the chemical composition of the neutral gas-phase molecules detected in the ambient atmosphere during the same period. The chemical composition of the ions was retrieved using an atmospheric pressure interface time-of-flight mass spectrometer (APi-TOF-MS) while the gas-phase neutral molecules (mainly sulfuric acid and HOMs) were characterised using the same mass spectrometer coupled to a nitrate-based chemical ionisation unit (CI-APi-TOF). Overall, we divided the identified HOMs in two classes: HOMs containing only carbon, hydrogen and oxygen and nitrogen-containing HOMs or organonitrates (ONs). During the day, among the ions, in addition to the well-known pure sulfuric acid clusters, we found a large number of HOMs clustered with nitrate (NO3-) or bisulfate (HSO4-), with the first one being more abundant. During the night, the distribution of ions, mainly composed of HOM clustered with NO3-, was very similar to the neutral compounds that are detected in the CI-APi-TOF as adducts with the artificially introduced primary ion (NO3-). For the first time, we identified several clusters containing up to 40 carbon atoms. These ions are formed by up to four oxidised α-pinene units clustered with NO3-. While we know that dimers (16-20 carbon atoms) are probably formed by a covalent bond between two α-pinene oxidised units, it is still unclear what bonding formed larger clusters. Finally, diurnal profiles of the negative ions were consistent with the neutral compounds revealing that ONs peak during the day while HOMs are more abundant at night-time. However, during the day, a large fraction of the negative charge is taken up by the pure sulfuric acid clusters causing differences between ambient ions and neutral compounds (i.e. less available charge for HOM and ON).

Changes in soil organic carbon fractions after remediation of a coastal floodplain soil.

PubMed

Wong, V N L; McNaughton, C; Pearson, A

2016-03-01

Coastal floodplain soils and wetland sediments can store large amounts of soil organic carbon (SOC). These environments are also commonly underlain by sulfidic sediments which can oxidise to form coastal acid sulfate soils (CASS) and contain high concentrations of acidity and trace metals. CASS are found on every continent globally except Antarctica. When sulfidic sediments are oxidised, scalds can form, which are large bare patches without vegetation. However, SOC stocks and fractions have not been quantified in these coastal floodplain environments. We studied the changes in soil geochemistry and SOC stocks and fractions three years after remediation of a CASS scald. Remediation treatments included raising water levels, and addition of either lime (LO) or lime and mulch (LM) relative to a control (C) site. We found SOC concentrations in the remediated sites (LO and LM) were more than double than that found at site C, reflected in the higher SOC stocks to a depth of 1.6 m (426 Mg C/ha, 478 Mg C/ha and 473 Mg C/ha at sites C, LO and LM, respectively). The particulate organic C (POC) fraction was higher at sites LO and LM due to increased vegetation and biomass inputs, compared to site C. Reformation of acid volatile sulfide (AVS) occurred throughout the profile at site LM, whereas only limited AVS reformation occurred at sites LO and C. Higher AVS at site LM may be linked to the additional source of organic matter provided by the mulch. POC can also potentially contribute to decreasing acidity as a labile SOC source for Fe(3+) and SO4(2-) reduction. Therefore, coastal floodplains and wetlands are a large store of SOC and can potentially increase SOC following remediation due to i) reduced decomposition rates with higher water levels and waterlogging, and ii) high C inputs due to rapid revegetation of scalded areas and high rates of biomass production. These results highlight the importance of maintaining vegetation cover in coastal floodplains and wetlands for sequestering SOC. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

In-situ determination of the oxidation state of iron in Fe-bearing silicate melts

NASA Astrophysics Data System (ADS)

Courtial, P.; Wilke, M.; Potuzak, M.; Dingwell, D. B.

2005-12-01

Terrestrial lavas commonly contain up to 10 wt% of iron. Furthermore, rocks returned from the Moon indicate lunar lava containing up to 25 wt% of iron and planetary scientists estimated that the martian mantle has about 18 wt% of iron. An experimental challenge in dealing with Fe-bearing silicate melts is that the oxidation state, controlling the proportions of ferric and ferrous iron, is a function of composition, oxygen fugacity and temperature and may vary significantly. Further complications concerning iron originate from its potential to be either four-, six- or even five-fold coordinated in both valence states. Therefore, the oxidation state of iron was determined in air for various Fe-bearing silicate melts. Investigated samples were Na-disilicate (NS), one atmosphere anorthite-diopside eutectic (AD) and haplogranitic (HPG8) melts containing up to 20, 20 and 10 wt% of iron, respectively. XANES spectra at the Fe K-edge were collected for all the melts at beamline A1, HASYLAB, Hamburg, using a Si(111) 4-crystal monochromator. Spectra were collected for temperatures up to 1573 K using a Pt-Rh loop as heating device. The Fe oxidation state was determined from the centroid position of the pre-edge feature using the calibration of Wilke et al. (2004). XANES results suggest that oxidation state of iron does not change within error for NS melts with addition of Fe, while AD and HPG8 melts become more oxidised with increasing iron content. Furthermore, NS melts are well more oxidised than AD and HPG8 melts that exhibit relatively similar oxidation states for identical iron contents. The oxidation state of iron for NS melts appears to be slightly temperature-dependent within the temperature range investigated (1073-1573 K). However, this trend is stronger for AD and HPG8 melts. Assuming that glass reflects a picture of the homogeneous equilibria of the melt, the present in-situ Fe-oxidation states determined for these melts were compared to those obtained on quenched glasses from different temperatures, when possible, using wet-chemical analysis (i.e., K-dichromate potentiometry). Both datasets agree reasonably well (within 10 %). References: Wilke et al. (2004) Chemical Geology, 213, 71-87.

A record of reversed polarity carries by the iron sulphide greigite in British early Pleistocene sediments

NASA Astrophysics Data System (ADS)

Hallam, D. F.; Maher, B. A.

1994-01-01

Palaeomagnetic measurements were made on samples extracted from a short sequence of early Pleistocene estuarine clays, now exposed in a sea cliff near Sheringham on the north Norfolk coast, UK. On the basis of earlier palynological work, these clays had been ascribed a Pastonian (late Tiglian) age. The clays show marked changes in colour, from reddish-brown at the top of the unit, to blue-grey in the middle, and grey-brown at the base. The palaeomagnetic data vary in close association with these colour changes. The top and basal brown clays show scattered normal directions of low intensity, while the middle blue clays show strongly clustered reversed directions, of much higher intensities. Some samples taken from the boundary between the middle blue clays and upper red clays show upon demagnetisation a normal overprint on a stable reversed polarity. Using high-gradient magnetic extraction, magnetic concentrates have been obtained from the strongly magnetic middle blue clays. The presence of iron sulphide minerals in these concentrates was identified using energy-dispersive X-ray analysis during scanning electron microscopy. More specifically, X-ray diffraction identifies greigite as the only detectable ferrimagnetic mineral in the magnetic concentrates. Rock magnetic measurements show clear qualitative differences in the magnetic mineralogies of the three clay subunits, but absolute identification of the magnetic mineralogy of the weakly magnetic upper and basal brown clays has not yet been possible. We interpret the sequence as a primary reversed polarity record. This record is carried by the iron sulphide greigate as a chemical remanence acquired during `syn'-depositional reduction of iron via the decomposition of organic material in these anoxic tidal clays. Subsequently, the upper and basl subunits of the clay have been oxidised by permeation of groundwater from the adjacent coarse-grained sediments. Most of the griegite in the oxidised margins of the clay has been altered as a result, to a new, less efficient magnetic recording material which thus carries a later, scattered, low-intensity, normal overprint.

Bitumen II from the Paleoproterozoic Here’s Your Chance Pb/Zn/Ag deposit: Implications for the analysis of depositional environment and thermal maturity of hydrothermally-altered sediments

NASA Astrophysics Data System (ADS)

Holman, Alex I.; Grice, Kliti; Jaraula, Caroline M. B.; Schimmelmann, Arndt

2014-08-01

The formation of sedimentary exhalative (SEDEX) Pb/Zn deposits is linked to ocean euxinia, but recent evidence suggests that ferruginous conditions may have dominated the deep ocean during the Middle Proterozoic, a maximum period for SEDEX distribution. Biomarkers of sulfate-reducing and sulfide-oxidising bacteria are valuable indicators of euxinic conditions in such settings. Organic matter (OM) from SEDEX deposits is often affected by alteration and/or migration, but OM entrapped within the kerogen/mineral matrix (Bitumen II) may be less affected than the freely-extractable OM (Bitumen I). We analysed Bitumen II from the Paleoproterozoic Here’s Your Chance (HYC) Pb/Zn/Ag deposit to find evidence of euxinic conditions in the depositional environment. n-Alkane distributions in Bitumen II are markedly distinct from previously-reported Bitumen I. Bitumen II contains long-chain n-alkanes (up to C36 or C38) and a strong even-over-odd distribution in a number of samples, which are 4‰ to 7‰ depleted in 13C compared to n-alkanes in Bitumen I and verified as indigenous by comparison with δ13C of isolated kerogen. These features are interpreted as evidence of sulfate-reducing and sulfide-oxidising bacteria, confirming that HYC was deposited under euxinic conditions. Bitumen II has the potential to reveal information from OM that is degraded and/or overprinted in Bitumen I. Commonly-used methylphenanthrene maturity ratios give conflicting information as to the relative maturity of Bitumens I and II. Bitumen I contains a far higher proportion of methylated phenanthrenes than Bitumen II. As Bitumen II is sequestered within the kerogen/mineral matrix it may have restricted access to the ‘methyl pool’ of organic compounds that can donate methyl groups to aromatic hydrocarbons. Parameters that include both phenanthrene and methylphenanthrenes do not appear suitable to compare the maturity of Bitumens I and II; hence there is no clear evidence that Bitumen II is of lower thermal maturity than Bitumen I.

Terminally Truncated Isopenicillin N Synthase Generates a Dithioester Product: Evidence for a Thioaldehyde Intermediate during Catalysis and a New Mode of Reaction for Non‐Heme Iron Oxidases

PubMed Central

McNeill, Luke A.; Brown, Toby J. N.; Sami, Malkit; Clifton, Ian J.; Burzlaff, Nicolai I.; Claridge, Timothy D. W.; Adlington, Robert M.; Baldwin, Jack E.

2017-01-01

Abstract Isopenicillin N synthase (IPNS) catalyses the four‐electron oxidation of a tripeptide, l‐δ‐(α‐aminoadipoyl)‐l‐cysteinyl‐d‐valine (ACV), to give isopenicillin N (IPN), the first‐formed β‐lactam in penicillin and cephalosporin biosynthesis. IPNS catalysis is dependent upon an iron(II) cofactor and oxygen as a co‐substrate. In the absence of substrate, the carbonyl oxygen of the side‐chain amide of the penultimate residue, Gln330, co‐ordinates to the active‐site metal iron. Substrate binding ablates the interaction between Gln330 and the metal, triggering rearrangement of seven C‐terminal residues, which move to take up a conformation that extends the final α‐helix and encloses ACV in the active site. Mutagenesis studies are reported, which probe the role of the C‐terminal and other aspects of the substrate binding pocket in IPNS. The hydrophobic nature of amino acid side‐chains around the ACV binding pocket is important in catalysis. Deletion of seven C‐terminal residues exposes the active site and leads to formation of a new type of thiol oxidation product. The isolated product is shown by LC‐MS and NMR analyses to be the ene‐thiol tautomer of a dithioester, made up from two molecules of ACV linked between the thiol sulfur of one tripeptide and the oxidised cysteinyl β‐carbon of the other. A mechanism for its formation is proposed, supported by an X‐ray crystal structure, which shows the substrate ACV bound at the active site, its cysteinyl β‐carbon exposed to attack by a second molecule of substrate, adjacent. Formation of this product constitutes a new mode of reaction for IPNS and non‐heme iron oxidases in general. PMID:28703303

Energy transfer in the Congo deep-sea fan: From terrestrially-derived organic matter to chemosynthetic food webs

NASA Astrophysics Data System (ADS)

Pruski, A. M.; Decker, C.; Stetten, E.; Vétion, G.; Martinez, P.; Charlier, K.; Senyarich, C.; Olu, K.

2017-08-01

Large amounts of recent terrestrial organic matter (OM) from the African continent are delivered to the abyssal plain by turbidity currents and accumulate in the Congo deep-sea fan. In the recent lobe complex, large clusters of vesicomyid bivalves are found all along the active channel in areas of reduced sediment. These soft-sediment communities resemble those fuelled by chemoautotrophy in cold-seep settings. The aim of this study was to elucidate feeding strategies in these macrofaunal assemblages as part of a greater effort to understand the link between the inputs of terrestrially-derived OM and the chemosynthetic habitats. The biochemical composition of the sedimentary OM was first analysed in order to evaluate how nutritious the available particulate OM is for the benthic macrofauna. The terrestrial OM is already degraded when it reaches the final depositional area. However, high biopolymeric carbon contents (proteins, carbohydrates and lipids) are found in the channel of the recent lobe complex. In addition, about one to two thirds of the nitrogen can be assigned to peptide-like material. Even if this soil-derived OM is poorly digestible, turbiditic deposits contain such high amounts of organic carbon that there is enough biopolymeric carbon and proteacinous nitrogen to support dense benthic communities that contrast with the usual depauperate abyssal plains. Stable carbon and nitrogen isotopes and fatty acid biomarkers were then used to shed light on the feeding strategies allowing the energy transfer from the terrestrial OM brought by the turbidity currents to the abyssal food web. In the non-reduced sediment, surface detritivorous holothurians and suspension-feeding poriferans rely on detritic OM, thereby depending directly on the turbiditic deposits. The sulphur-oxidising symbiont bearing vesicomyids closely depend on the reprocessing of OM with methane and sulphide as final products. Their carbon and nitrogen isotopic signatures vary greatly among sites and could reflect the intensity of the anaerobic oxidation of methane (AOM) in the sediments. Within the vesicomyid habitats, the heterotrophic fauna exhibits a distinctively light carbon isotopic signature in comparison to the background sediments, clearly indicating the utilisation of chemosynthetically-derived OM. Fatty acid biomarkers further confirm that dorvilleid polychaetes consume aggregates that perform AOM. Terrestrial OM reprocessing by microbial consortium thus ensures its transfer to the benthic food web in the Congo deep-sea fan.

Experimental production of indicators for microbial sulfur metabolism in the Chelyabinsk LL5 chondrite: meteorites as standards for biomarker detection on Mars

NASA Astrophysics Data System (ADS)

Tait, A. W.; Wilson, S. A.; Tomkins, A. G.; Gagen, E. J.; Southam, G.

2016-12-01

One hurdle to finding evidence for life beyond Earth is being able to identify its chemical, textural and isotopic fingerprints. This is a challenge in environments that can mask biomarker discovery and/or where geochemical and mineralogical limits are still being established. An ideal solution would be to use standards with known chemical and isotopic compositions to reduce/remove any ambiguity of detection. We propose that chondritic meteorites are ideal standards. Chondrites have narrow ranges in mineralogical, chemical and isotopic compositions, including δ34S values. As such, they could preserve biomarkers of theorized sulfur-based metabolisms on Mars. Here, we demonstrate that bacteria can alter the chemistry of chondrites in a detectable and recognisable manner. We exposed polished fragments of the Chelyabinsk LL5 chondrite to an inoculum of the sulfur/iron oxidising bacterium, Acidithiobacillus ferrooxidans. Cell counts and aqueous sulfate concentrations were recorded over the course of a month. Meteorite samples were taken after one, two and four week exposures for FEG-SEM and FIB-SEM imaging, XRD phase analysis, and stable isotope (δ34S) geochemistry. Our electron microscopy work shows that bacteria and associated extracellular polymeric substances coat grains of troilite (FeS) and FeNi alloys. Decreasing aqueous sulfate concentrations, compared to increasing sulfate in abiotic controls, suggests that A. ferrooxidans may have been assimilating the sulfur released by oxidation of troilite. Also, low abundances of secondary minerals that are capable of recording biological fractionation of stable sulfur and/or iron isotopes were also produced: rozenite, gypsum, goethite, lepidocrocite, and jarosite, and may explain the reduction in soluble sulfur. Our FIB-SEM results show that nutrients (e.g., carbon, sulfur and nitrogen) become concentrated in layers at the surfaces of troilite and FeNi alloys within 1 week of incubation. These nutrient-rich regions are encased and preserved beneath mm-scale efflorescences of Fe-oxyhydroxide minerals, essentially fossilizing them. Meteorites that have landed on the surface of Mars are therefore favourable targets for future sample return missions, because they can record unambiguous evidence of a putative biosphere in multiple ways.

Microbial nitrogen transformation potential in surface run-off leachate from a tropical landfill

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mangimbulude, Jubhar C.; Straalen, Nico M. van; Roeling, Wilfred F.M., E-mail: wilfred.roling@falw.vu.nl

2012-01-15

Highlights: Black-Right-Pointing-Pointer Microbial nitrogen transformations can alleviate toxic ammonium discharge. Black-Right-Pointing-Pointer Aerobic ammonium oxidation was rate-limiting in Indonesian landfill leachate. Black-Right-Pointing-Pointer Organic nitrogen ammonification was most dominant. Black-Right-Pointing-Pointer Anaerobic nitrate reduction and ammonium oxidation potential were also high. Black-Right-Pointing-Pointer A two-stage aerobic-anaerobic nitrogen removal system needs to be implemented. - Abstract: Ammonium is one of the major toxic compounds and a critical long-term pollutant in landfill leachate. Leachate from the Jatibarang landfill in Semarang, Indonesia, contains ammonium in concentrations ranging from 376 to 929 mg N L{sup -1}. The objective of this study was to determine seasonal variation in themore » potential for organic nitrogen ammonification, aerobic nitrification, anaerobic nitrate reduction and anaerobic ammonium oxidation (anammox) at this landfilling site. Seasonal samples from leachate collection treatment ponds were used as an inoculum to feed synthetic media to determine potential rates of nitrogen transformations. Aerobic ammonium oxidation potential (<0.06 mg N L{sup -1} h{sup -1}) was more than a hundred times lower than the anaerobic nitrogen transformation processes and organic nitrogen ammonification, which were of the same order of magnitude. Anaerobic nitrate oxidation did not proceed beyond nitrite; isolates grown with nitrate as electron acceptor did not degrade nitrite further. Effects of season were only observed for aerobic nitrification and anammox, and were relatively minor: rates were up to three times higher in the dry season. To completely remove the excess ammonium from the leachate, we propose a two-stage treatment system to be implemented. Aeration in the first leachate pond would strongly contribute to aerobic ammonium oxidation to nitrate by providing the currently missing oxygen in the anaerobic leachate and allowing for the growth of ammonium oxidisers. In the second pond the remaining ammonium and produced nitrate can be converted by a combination of nitrate reduction to nitrite and anammox. Such optimization of microbial nitrogen transformations can contribute to alleviating the ammonium discharge to surface water draining the landfill.« less

Assessment of antioxidant activity by using different in vitro methods.

PubMed

Schlesier, K; Harwat, M; Böhm, V; Bitsch, R

2002-02-01

In this study, six common tests for measuring antioxidant activity were evaluated by comparing four antioxidants and applying them to beverages (tea and juices): Trolox equivalent antioxidant capacity assay (TEAC I-III assay), Total radical-trapping antioxidant parameter assay (TRAP assay), 2,2-diphenyl-l-picrylhydrazyl assay (DPPH assay), N,N-dimethyl-p-phenylendiamine assay (DMPD assay), Photochemiluminescence assay (PCL assay) and Ferric reducing ability of plasma assay (FRAP assay). The antioxidants included gallic acid representing the group of polyphenols, uric acid as the main antioxidant in human plasma, ascorbic acid as a vitamin widely spread in fruits and Trolox as water soluble vitamin E analogue. The six methods presented can be divided into two groups depending on the oxidising reagent. Five methods use organic radical producers (TEAC I-III, TRAP, DPPH, DMPD, PCL) and one method works with metal ions for oxidation (FRAP). Another difference between these tests is the reaction procedure. Three assays use the delay in oxidation and determine the lag phase as parameter for the antioxidant activity (TEAC I, TRAP, PCL). They determine the delay of radical generation as well as the ability to scavenge the radical. In contrast, the assays TEAC II and III, DPPH, DMPD and FRAP analyse the ability to reduce the radical cation (TEAC II and III, DPPH, DMPD) or the ferric ion (FRAP). The three tests acting by radical reduction use preformed radicals and determine the decrease in absorbance while the FRAP assay measures the formed ferrous ions by increased absorbance. Gallic acid was the strongest antioxidant in all tests with exception of the DMPD assay. In contrast, uric acid and ascorbic acid showed low activity in some assays. Most of the assays determine the antioxidant activity in the micromolar range needing minutes to hours. Only one assay (PCL) is able to analyse the antioxidant activity in the nanomolar range. Black currant juice showed highest antioxidant activity in all tests compared to tea, apple juice and tomato juice. Despite these differences, results of these in vitro assays give an idea of the protective efficacy of secondary plant products. It is strongly recommended to use at least two methods due to the differences between the test systems investigated.

Grey water treatment at a sports centre for reuse in irrigation: a case study.

PubMed

Gabarró, J; Batchelli, L; Balaguer, M D; Puig, S; Colprim, J

2013-01-01

Grey water has long been considered a promising option for dealing with water scarcity and reuse. However, factors such as lack of macronutrients and low carbon content make its treatment challenging. The aim of this paper was to investigate the applicability of sequencing batch reactor (SBR) technology to on-site grey water treatment at a sports centre for reuse in irrigation. The results demonstrated that the regenerated water complied with microbiological parameters concerning restriction of solids and organic matter removal. Denitrification was not fully accomplished, but ammonium was totally oxidised and low concentrations of nitrates were achieved. Effluent with good appearance and no odour was used in an experimental study to irrigate a grid system containing natural and artificial grass sections. The conclusion is that SBR technology offers a promising treatment for grey water.

Syntrophic acetate oxidation in industrial CSTR biogas digesters.

PubMed

Sun, Li; Müller, Bettina; Westerholm, Maria; Schnürer, Anna

2014-02-10

The extent of syntrophic acetate oxidation (SAO) and the levels of known SAO bacteria and acetate- and hydrogen-consuming methanogens were determined in sludge from 13 commercial biogas production plants. Results from these measurements were statistically related to the prevailing operating conditions, through partial least squares (PLS) analysis. This revealed that high abundance of microorganisms involved in SAO was positively correlated with relatively low abundance of aceticlastic methanogens and high concentrations of free ammonia (>160 mg/L) and volatile fatty acids (VFA). Temperature was identified as another influencing factor for the population structure of the syntrophic acetate oxidising bacteria (SAOB). Overall, there was a high abundance of SAOB in the different digesters despite differences in their operating parameters, indicating that SAOB are an enduring and important component of biogas-producing consortia. Copyright © 2013 Elsevier B.V. All rights reserved.

Diazonium Functionalisation of Carbon Nanotubes for Specific Orientation of Multicopper Oxidases: Controlling Electron Entry Points and Oxygen Diffusion to the Enzyme.

PubMed

Lalaoui, Noémie; Holzinger, Michael; Le Goff, Alan; Cosnier, Serge

2016-07-18

We report the controlled orientation of bilirubin oxidases (BOD) from Myrothecium verrucaria on multiwalled carbon nanotubes (MWCNTs) functionalised by electrografting of 6-carboxynaphthalenediazonium and 4-(2-aminoethyl)benzenediazonium salts. On negatively charged naphthoate-modified MWCNTs, a high-potential (0.44 V vs. SCE) oxygen reduction electrocatalysis is observed, occurring via the T1 copper centre. On positively charged ammonium-modified MWCNTs, a low-potential (0.15 V) oxygen reduction electrocatalysis is observed, occurring through a partially oxidised state of the T2/T3 trinuclear copper cluster. Finally, chemically modified naphthoate MWCNTs exhibit high bioelectrocatalytic current densities of 3.9 mA cm(-2) under air at gas-diffusion electrode. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.